Category: Basic Gunsmithing Skills

 

 

Professional Scope Mounting

 

Don’t be deceived by what looks to be a simple job. Professional scope mounting takes training and a good working knowledge of gunsmithing to get the most out of the combination of gun, scope, mounts and ammo. Maybe the sporting goods store has a stock boy that can tighten down #6 screws tighter than the space shuttle’s gas cap but there is a lot more to this job than just making sure it is tight.
Let’s define a few terms before we go any farther to keep the confusion to a minimum

Ring- This is the round clamp that goes around the scope and has an arrangement on the bottom to attach it to the base.

Base- The small unit that attaches to the gun (usually with screw but not always) and provide a means for the ring to attach.

Eyepiece- the end of the scope next to shooters eye ( usually sharper than necessary!)

Objective end- The opposite end of the scope from the eyepiece. Measured in millimeters

Parallax- An error in viewing two object from different locations. Hold up your finger and look at the tip and the wall behind it, now move your eye around and the finger appears to move against the wall. This happens in the rifle scope when you look at a close target (like 25 yards) and move you head position on the comb of the stock. The crosshairs appear to move on the target. It can be adjusted to match the target distance or for most factory hunting scopes it is factory adjusted at 125 yards. It is basically a short range problem.

Picatinny- A military standard for a scope base similar to the weaver style. Weaver bases will attach to a Picatinny rail but Picatinny rings and devices will not fit on the Weaver base. If using a weaver ring on a Picatinny base it should be slide forward before the ring is tightened on the base. Even though weaver rings work this is not a desirable setup. Best to have the base match the ring. While originally a scope base these are used for almost any device being attached to a rifle like night vision equipment, flashlights or lasers.

Zero- A setting on the scope or sights that will align the aiming point and the strike of the bullet.

MOA- abbreviation for minute of angle. It equals roughly one inch at 100yards, two inches at 200, 5 inches at 500, and so forth. This also means it equals ½ inch at 50 yards, ¼ inch at 25 and so forth. So if your scope will move you ¼ minute per click then one click will move you 1/16 inch at 25 yards or 2.5 inches at 1000 yards. Read this over or draw it out with a straight edge or whatever you need to do but you have to understand MOA. When you want to move a scope that is centered 20 MOA to the left and the mounts are 3.8 inches apart it will require a good understanding of MOA!

Power- Usually denoted by a number followed by an X like 6X or many times in combination with the objective lens size like 6X42 would be a 6 power scope that has a 42 millimeter objective lens. Variable scopes have an adjustable setting and fixed scopes are only one power.

Collimator- A device to make a parallel line up. Used by the gunsmith to align the aiming point with the center of the bore. While it does not sight in the firearm it is a very useful tool allowing the gunsmith to see how precisely the scope adjustments move the aiming point and determine how much backlash is present.

Reticle- A system of fine lines used to aim. (Duh! It’s the crosshairs)

Mill Dot- A system of dots spaced on the reticle lines used to measure range.

Windage- Movement from left to right or horizontal

Elevation- Movement up and down or vertical.

Drop- usually a measurement in inches of the path of the bullet in relation to the line of sight reflecting the effect of gravity on the projectile.

Selecting the ring and base combination that is right for the job will be the first hurdle. A quick look at the current Brownells catalog reveals 20 pages of scope rings and bases. One piece, two piece, Weaver, Leupold, Picatinny, See-thru, Unertl and many more can make it hard for the person that doesn’t know what they want. Maybe we need to clarify just what a good scope mount should do. Hold the scope securely in line with the position of the eye when the gun is mounted to the shoulder and return to the same place (zero) if it is removed and reinstalled. Being adjustable so the scope adjustments can remain close to center would be nice too. Most of the available mounting systems have something to offer. The old Weaver mounts are solid and return close to zero, The Old Redfield system is harder to remove and return to zero but it is adjustable for windage.

After selecting take a look at what will be holding the bases to the firearm. In most instances it will be screws. Overwhelming favorite is the 6×48 with the 8×40 gaining ground. The 6 is a wire gauge size and the 48 is the number of threads per inch. These small screws have proven adequate for many years, however as firearms have become more powerful and scopes larger the effects of recoil that must be endured by the screws that are responsible for holding it all together have raised the strength requirements. Poor screw fit due to being too long or too short has created the majority of problems associated with scopes but it doesn’t end there. Screw head diameter and wrong threads have also been real pain for the gunsmith trying to turn out quality work. These problems are usually avoided by buying quality mounting products. Even if you buy the best it is still a good practice to inspect all the parts for defects before assembling on the gun. Look close and make sure threads are there and that they go all the way to the bottom of the hole. Try the screws in the holes and make sure they are not loose if you wiggle from side to side.

After you are satisfied with the fit and quality of the bases and the length and fit of the screws it is time to attach them to the gun. Take your time and snug each screw individually and then check the base for tightness to the gun. This step is important to make sure all the screws are actually holding the base to the gun and not coming tight without the head of the screw resting against the base. After you are satisfied each screw is performing like it should you can tighten. Judgment and experience are a great help here but nothing really beats a torque wrench. Thirty inch pounds is plenty of pressure with a 48 thread.

While I don’t prefer Loctite on my guns some of my customers swear they need it so I comply with their wishes. Personally I would rather be able to check screw tightness later and know the screw is actually tight against the base and not just being held by the Loctite in the threads.

If this is a custom job or a cobbled together arrangement I will use a long straight edge on the bases to check alignment with the end of the barrel. With the straight edge resting on both bases it should parallel the bore and be taking a path of its own. This is easy to see with the straight edge by the time it gets to the muzzle but a small misalignment is very hard to detect when the front and rear bases are only a couple inches apart.

Now we can cycle the action and make sure the action works freely. If any screws are protruding into the receiver and impinging on working parts you will probably feel it but close inspection is still warranted to make sure there is no contact with the bolt that might affect accuracy by disturbing alignment.

When all is well we can proceed to mounting the rings. I usually start with the front ring only and after mounting it snugly I will check ring height by placing the scope in the ring to make sure it clears the barrel. Then I use a long piece of round stock to check alignment with the bore. With the front ring in place the round stock which is no more than a long piece of aluminum rod long enough to extend from the rear of the receiver to the end of the barrel should be centered directly over the bore. If there is an alignment problem solve it by fitting or replacing before proceeding. Next the rear ring can be positioned using the round stock as a guide. Tighten the rear ring while watching the position of the round stock over the bore. It should not move. Again if there is an alignment problem solve it before continuing.

Now we have rings in line with the bore so they will they will not damage or kink the scope tube when they are tightened on the fragile scope tube. Another problem we are trying to avoid is placing any stress on the receiver from ring misalignment. This can be detrimental to accuracy just like a bedding problem would place stress on the receiver from beneath the action.

Now we have properly aligned and tight bases with rings in line with and parallel to the bore but we are still not quite ready to mount the scope. Our next job is make sure the individual bore of each ring is in alignment. We do this by lapping with a brass rod the size of the scope body (1 inch or 30 mm) coated with an abrasive lapping compound. The caps or tops are tightened only enough to contact the rod but allow movement so the twisting and front to rear movement of the lapping rod can proceed. When the two materials are rubbed together the abrasive will cut away the material in contact with the rod. If the rings are in perfect alignment (you wish!) the wear will show a pattern inside the ring of finish being removed on the entire surface. A normal result will be 20% of the finish removed after several minutes of lapping. For most installations getting the lapping above 60% will be a good fit. Since this is a fitting operation the rings and caps are now a fitted pair and should be marked in some manner to make sure they are not mismatched. This includes marking the cap not only as to which ring but also to prevent reversing the cap.

Whew! I told you it wasn’t easy but now you can clean off the lapping compound and mount the scope. All you have to do is get it straight in the rings and tighten without it moving and have it end up exactly where the customer wants it. Yes, in the end it is the customer that needs to be happy so with the job so at this point I usually leave the scope loose in the rings until the customer arrives to make the final determination as to how where it needs to be tightened. You might try to coach them a little by explaining the need for adequate eye relief and how if the scope is a little forward the head will come to a more consistent position on the stock and consistency leads to better shooting but in the end make the customer happy.

Using a scope reticle leveling device will stop a lot of disputes as you tighten the scope and hand it back and forth for the customer to check. These are fairly inexpensive and available from Brownells and others. Many people cant the gun without realizing it and nothing you can do will make them happy but putting the crosshairs level for them. Thankfully this isn’t a problem in most hunting situations since the distance is close and the target large in relation to a long range target and if the customer is a long range shooter they will already be schooled in the effects of misalignment.

This might seem like a lot of trouble but it really doesn’t take that much time after you have done a few and it just seems like a shame when all the work that went into an accurate rifle is compromised with a poor scope mounting job. I find writing up directions and handing out copies to customers that plan on mounting their own scope will generate a lot of scope jobs as the customer gains a better understanding of the importance of the job. As always, DO GOOD WORK!

 

 

Working on Rimfires

 

If your business is to survive you can never forget that you have to do more than fix guns, you have to make a profit. Working on rimfires can make this hard or impossible. Built from the cheapest of materials and many times poorly designed they can be a real time consumer for the gunsmith.

The average rimfire that is brought in for service has been shot thousands of times without cleaning and when it finally jammed the stuck round was pried free with pliers and screwdriver. The delicate feed mechanism that was formed from soft steel sheet metal or plastic now looks like it was hit by a drunk driver. All the other working parts are worn badly as well and the whole thing is a mess. Of course it didn’t cost much so don’t let the bill go over $40 without calling. Try to turn away these jobs as much as possible but some will be unavoidable. I’m not talking about Old Winchesters, Marlin 39s and Rugers here but you will quickly know which ones you need to avoid.

Make sure your customer understands you have to charge for your time and how extensive the work will be before proceeding. You will have customers that will not understand why it cost more to fix that it cost to purchase new and it is best to resolve this before investing your time and money. Yes there will be customers that have a special gun that was in the family and they want to fix it up for the grandkids or just memories but sometimes it just makes more sense to turn it into a wall hanger.

Also understand that if you do a repair on one of these worn out oldies it will be your baby from then on. The story that will be told was “ I carried to the local gunsmith and it hasn’t worked right since”. It won’t matter that you replaced the extractor last month and now the trigger is slipping, it will just be your fault you couldn’t even keep a 22 working. Remember a happy customer tells 1 and an unhappy customer tells 10!

OK you couldn’t avoid it and you have to work on it what do you look for?

Chamber damage– Make sure a firing pin that is too long or unrestrained and has not peened the edge of the chamber when the gun was dry fired. If the chamber is peened from the pin striking it has pushed up a burr into the chamber and will not be able to extract when it fires. If you cut this burr away the recess it leaves will be behind the case rim where the firing pin hits and the rim will not crush the priming compound. Better to iron out the burr with a chamber iron or a smooth tapered pin which will push the metal back into the recess formed from the strike of the firing pin on the chamber edge. Look at the chamber itself and a fired case to determine if the chamber has enlarged or swelled. Make sure the barrel has not slipped forward in the receiver and increased headspace .

Extractor– Check for wear or breakage. Maybe reshaping will improve functioning. Make sure it doesn’t catch on the chamber recess and its movement over the cartridge rim is without problems.

Feed mechanism or throat–See that it releases the cartridge at the correct time in the cycle and has not been deformed. Make sure that the cartridges are moved out of the throat and into the chamber without undue pressure or deforming the bullet. Remember it is a rimfire and can fire when the bolt strikes the rim to feed it into the chamber so proceed with caution!

Firing pin– Make sure the tip is correct shape and protrusion within normal limits. The best design will strike just inside the rim and not on the edge. This probably won’t matter unless it is a target rifle as long as it has sufficient force to crush the rim. If the rim is not supported by the chamber the pin strike will not be able to get good ignition. Dirt and powder residue accumulate in the firing pin recesses and cause light hits and misfires.

Trigger– Dirt and wear are the problems here. Trigger and sear notches wear down and need to be recut. If the original part was case hardened then your repair will not last unless you restore the surface hardness by carburizing and heat treating. Always check safety function when doing any work and make sure the gun will withstand several taps with the plastic hammer without firing. This can simulate the gun being dropped.

Magazines– Always a problem. Removable clips are easily lost and replacements are hard to find. Tube magazines are harder to lose but the internal springs break and rust and small dent will impinge on the follower and prevent it from working. Replacements are best but rebuild kits are available from Brownells.

Ammo– Lots of variation in ammo. Make sure the customer understands how to let the gun tell him which one it likes. This is easier than the other way around. Standard velocity, high velocity and hyper velocity all perform differently.

Remember all guns have the same basic cycles. Loading, feeding, firing, extraction and ejection are all required to be flawless. A good understanding of the cycle of operation and a thorough examination of the action will usually show what needs to be done. Work through each process and test fire thoroughly. Regular church attendance will also help ( at least with the cussing)

 

Accuracy Testing

 

The gunsmith needs a working knowledge of accuracy testing to be competent in rifle work. After all it doesn’t matter whether it is a target, tactical, hunting or plinking model, if it is a rifle or pistol it has to be accurate to be interesting. While the intrinsic accuracy of the firearm is usually the focus, this is always intertwined with ballistics to achieve the end result of a hit on target. The standard definition of a rifle is a firearm that fires a single projectile through a rifled bore to the place the sights are aligned. Sounds easy enough, unless something goes wrong. Chances are if you are interested enough to read this you already know that a lot of things go wrong every shot. Your job is to find a way to eliminate these errors or at least mitigate their effects to get a grouping of shots close enough together to satisfy the shooter.
Ever wonder exactly what you learned when you shot that group of three with all holes touching? Did you learn just as much on the next group with two in one hole and the third a sickening two inches away. Maybe you did without realizing it. A lot of shooters fire thousands of rounds without stopping to think about what the groups display. The rifle is telling you a story and you need to know how to listen.
The rifle is telling you what size the cone of fire is for the ammunition. It is a term you are probably not familiar with but every rifle has a cone of fire or area where the bullets will impact. This undetermined area is defined by firing several shots with as little deviation as possible. Now you don’t have to be a math whiz to know that if you have an unknown area and select three random points inside that area it will never be an accurate representation of that area but this is the norm when it comes to rifle testing. Does this mean you need to fire 100 round groups? No, don’t go off the deep end. First lets look at what we are trying to do.
With any range testing scenario we want to duplicate what the rifle will be doing when it is working or doing the job it was built to do. A deer rifle for a still hunter lives around the concept of one shot fired from a cold ( sometimes very cold!) barrel. The data you get from three shots might not be an accurate picture of what this gun will do the next three times this gun is fired in a hunting scenario. For the average weight barrel in a highpower rifle the temperature change is probably 40-50 degrees between shots. Combine this with the understanding that three random points are no better than a 36% representation of the group. For this rifle we need to define the group with more shots but all fired from a cold barrel. Preferably fired in the same ambient temperature as the hunt. While this might not be possible just be aware of what is best. Rifles and ammo can behave differently with a big temperature change.
So you go to the range and take a long time between shots, fire several rounds, and have good data, but what if the rifle will be used with a hot barrel? My match rifle has to shoot ten shot rapid fire strings. So doesn’t matter about cold barrel zero. Wrong! To get the most out of the rifle you need to know where that first shot is going. Careful testing and record keeping will tell you if your rifle will need adjustment after the first few shots. My best 600 yard rifle required me to come down a full minute after firing the second sighter. This is a big move to make when the first 2 are in the x ring but keeping a data book proved it. Careful record keeping and tracking will pay off.
For most of us accuracy testing will be shooting off the bench. If you think this doesn’t require skill you are misinformed. If you have never had any instructions in bench technique you need to understand you are shooting a tuning fork.

 

 

Working with Gunstocks

 

Working with gunstocks comes with the territory for the gunsmith. For some it is what they wish they could do all the time, others might be happier if guns didn’t have stocks. Personally I enjoy stock work but I don’t seem to make much money when I do. It just seems that there are not many shortcuts when it comes to quality stock work. Maybe having a business plan would be a good idea so you would know what to avoid and what to seek. Of course if you love the smell of walnut and the beauty of a feathered crotch (I’m speaking of a type of walnut!) you have found your place in life and will soon be famous for things of beauty. Let’s break our work down and look at the jobs that frequently come in the gun shop.

Fitting guns is a term used to explain changing the stock dimensions to fit a particular shooter. This line of work requires a thorough understanding of shotgun shooting as well as the gunsmithing skills involved in changing drop, length of pull, pitch and cast off. These specialist are usually in attendance at major shooting events and do a brisk business while there. Many times the fitter will have a try gun which is a shotgun with an adjustable stock so the shooter can adjust and try until he finds the perfect combination of drop, pull and cast. Then the dimensions are measured and recorded so the shooters personal gun can be modified. Attending one of these events is always beneficial and can open up opportunities for learning as well as future business.

Recoil pads and sling swivels are two of the jobs that show up frequently in the shop. While these two jobs seem simple they are high in nuisance value and anything but perfect work will show up and make you look like a novice or worse. Both of these jobs also carry the risk of damaging a fine stock so a little extra for insurance might be a good idea.

The sling swivels must be installed on center and secure but without any chance of splitting. Choose a drill that slightly smaller than the core of the screw you will be installing. Counter sink this hole at least 3/8” with a drill that matches the outside diameter of the screw. This helps prevent the screw from pulling up the wood as it tries to pull itself into the wood. Apply steady pressure downward while starting the screw for best results. For the swivels that have a nut on the back like on the forearm make sure it doesn’t contact the barrel. Also make sure to secure the swivel in the nut so it cannot possibly come out. This is a potential disaster when the swivel breaks and the rifle swings around while the shooter grabs to stop it. A drop of locktite or epoxy on the threads should do the trick.

Most of the time before you can fit a recoil pad you have to cut the stock to length or at least flatten the surface. Seems everybody has a different method for this and you will have to pick something you are comfortable with. For sure it is a lot easier to cut than put back so make certain of your measurements. Length of pull is measured from the trigger to the middle of the pad. Pitch is easier to determine by placing the gun butt down against the wall or vertical straight edge and measuring the muzzle deviation from the vertical. Most guns have a little negative pitch. This allows the butt to slide onto the shoulder without the top edge dragging and makes for more consistent gun mount. Measure other stocks and try them out on the customer. After all the idea is to fit the gun to the customer. I use masking tape and mark my cut with a marking scribe that holds a pencil and cut with a very fine cut hand saw. By letting the saw do the work with minimum pressure and holding both parts until the cut is done I get excellent results. Cutting through the tape help to minimize the saws effect on the finish and make for a smoother edge. Find the cutting method you prefer and practice on old stocks. You want to be confident before that customer comes in with the Superposed grade 12 and wants it 5/16 shorter with 1 3/8 pitch.

I cringe when I read some of the old instructions for installing recoil pads. Some of them actually recommend grinding the pad while it is on the stock. Never try this on a customer’s stock. There are several jigs that allow you to set the angle on the pad and hold it securely for grinding while the pad is attached to the jig. Practice on old stocks by cutting off the stock and refitting the old pad. The more pads you grind and fit the better your skills. This is a much safer way to learn as opposed to wrecking a customer’s stock. Don’t forget to seal the end of the freshly cut stock. The customer will thank you after he spends the day hunting in the rain. Just go slow and allow the sander to cut the pad. If you hurry heat will build and the pad will smear. The finished job should follow the lines of the stock and not have overhang or undercut. Most pad manufacturers have instruction for grinding their pads. They know what works best for their product and their instructions will help you get a great job. If the old screw holes in the stock interfere with alignment of the new pad then drill then out oversize and epoxy a hardwood dowel in the hole. After epoxy has hardened cut off flush and start over with new wood.

It seems that I am seeing more shooters lately seeking recoil reduction with the stock mounted recoil reducers. These are sealed units that have moveable weight inside that distributes the recoil force over a longer time period which takes the peak out of the recoil cycle. If the unit has mercury for the weight remember that the unit only works if the muzzle is pointed up so the mercury is in the back. Don’t put this type in a rifle that will be used from a tree stand. Some of these use the bolt hole already in the stock but you can also drill a hole for it if needed. These are large holes and require careful layout. Additional units can be installed in a recess routed into the forearm under the barrel. This can also balance out the gun but does add a little weight.

Glass bedding is very popular but not very well understood. While I don’t want to write another “how to” about bedding I think it might be more beneficial to go into why. For a rifle to shoot the same spot every time the receiver must rest in the same place in the stock every time. It should be a home without stress but secure enough maintain the gun in this perfect cradle. Before we had epoxy this was really hard to achieve with a wood to metal fit. Wood expands and contracts with the temperature and humidity. Epoxy to the rescue. While liquid it conforms perfectly and hardens to the mirror image of the receiver. Pop out the receiver, trim of the excess, reinstall the missing parts, and you are done. But does it shoot any better?

If the problem was wandering zero or the gun wouldn’t stay sighted in then maybe, but if it didn’t group at all it probably still won’t. For sure epoxy bedding will help and never hurt accuracy it won’t cure problem in other areas. If the problem is a bad barrel then all the epoxy in the world won’t help.

So you have decided to glass bed but which type is best? Do you want to pillar bed? Which type of epoxy? Which release agent? A lot of questions but with a little information you can make the best selection. Select the epoxy that is the easiest to use. I like Acra gel from Brownells. Mixes one to one with plenty of working time and stiff enough to stay put. Spray release from Brownells is the best release agent I ever used. No cleanup, easy to apply and fast. Just don’t forget to use it!

 

Drilling Holes in Firearms

 

 

The man comes into the gun shop and ask “How much to drill and tap a couple of holes in my rifle”. Ten dollars for the holes, fifteen for the threads and twenty for putting them in the right spot the first time! Then you need to smile and make sure you didn’t make him mad but you really told the truth. Like so many machine shop operations it is the setup that really eats up the time and requires the knowledge.

Normally we are talking scope mounts when drilling and tapping so it is like putting pistol sights on a 25 auto that will be sighted in at 200 yards. Huh? Look at the front and rear scope bases, now imagine they are a front and rear sight. Just like adjusting sights, the closer they are together the more the bullet impact is shifted. Most modern scope mounts will move the bullet one minute of angle when the base is moved .002″. A hair from your head will usually measure .005 so to center a scope on a rifle literally requires you to do better than splitting a hair!

Maybe the first job is to decide if the gun should be drilled and tapped at all. If the gun has true collector value it might be wise to leave it as is. Old Winchesters and such will lose value if modified in any way. Still some owner will insist on mounting a scope and after all it is their gun. Just do your best to let the owner know so they can make an informed decision.

Next is the actual layout and selection of mounts and bases. The cheapest is rarely the best and this applies to mounts as well. Try to select something that will look good and hold securely. Most of the time the owner preference will be the deciding factor but you might be able to guide him to a better choice if you are well informed. Most manufacturers supply charts to tell you which model base fits which firearm. Be aware that sometimes the are slight differences between models that can require a different mount. Sometimes you can modify bases for special applications or the correct things that went wrong from the past like a hole drilled off center.

Now you have the scope, bases, rings and barreled action. This would be a good time to center the reticule in the scope. Find a small cardboard box and notch the sides so the scope will rest in the notches with the adjustment knobs between the notches. Now slowly rotate the scope tube while looking through the scope at a distant object. When you have adjusted the scope so that the center of the reticule no longer moves as the body is rotated the reticule is centered. This is important because the scope performs best when you are looking through the center and it leaves plenty of adjustment for sighting in.

Now you can layout the bases on the receiver and make sure the bases look correct and the holes to be drilled will not be in bad locations like on the face of the bolt lug shoulder or through a working part attached to the top of the receiver. A lot of 22 rifles have bullet guides and such mounted in the top that can be avoided by moving the front or back a small amount. Just make sure the final location you select will work with the scope. Sometimes an extension ring can solve problems with base spacing. Using a pencil or tiny scribe marks go ahead and mark the locations of the bases for a reference.

If you have a Forster jig for drilling and tapping you can mount it on the drill press or milling machine and follow your directions for securing the barrel action and the jig to the machine. I can’t imagine doing this type work professionally without this jig. It make jobs that are difficult almost easy and saves so much time that it easily pays for itself in a few jobs. I have looked at other jigs through the years but have not found one that equals the Forster. Not saying there isn’t one but I haven’t seen it. It makes sure the holes are drilled in reference to the center of the barrel, makes sure the hole spacing is correct, makes sure the tap is held straight and serves as a depth stop for holes that can go all the way through. While holes that go through are preferred because broken taps can be removed a little better sometimes it isn’t possible and can be extremely dangerous to go through. A screw going into a chamber can turn a 6/48 base screw into a bullet that will go through a scope body and can injure a shooter. I have seen this more than once!

If you don’t have a jig of any type and are determined to drill and tap anyway I have a method for that too. Assemble the rings and bases to the scope you centered earlier. Now set the assembly on the receiver where you want it to go. A collimator or boresighter can should be used to make sure all is properly aligned. If you don’t have a bore sighting device you can look through the bore at a distant object and align the scope accordingly. Don’t forget if this is a long range target gun that you might want to allow for extreme drop. Many long range bases have 20 minutes of elevation built in the base. After making sure it will work in this location mix up a little five-minute epoxy. Now place a small dot of this epoxy between the receiver and base and don’t disturb until tomorrow. Yes, it said five minute but you want the maximum strength. Now remove the rings from the bases. Now select a drill the size of the screw heads and lightly turn this in the screw holes in the base. This will remove the extra epoxy and mark the center of the hole in the base on the receiver with a small start on the hole on the receiver. Now pop off the epoxied base with a plastic mallet and the receiver is ready to be drilled. The holes are started and it is fairly simple to keep the drill in the right location.

This jobs are high in nuisance value and eat up considerable time for the gunsmith. They also carry the threat of a lot of bad publicity if done poorly. Thankfully it has become a rare job for the gunsmith but it still shows up at the gunshop from time to time so a gunsmith will need to master getting holes in the right location. Remember it is less than splitting a hair! Do good work!

 

Timothy P. Whealton

 

 

What is Headspace and why is it important?

Headspace is the amount of space in the chamber from the face of the bolt when it is locked in firing position to whatever stops a cartridge when it is dropped into the chamber. Actually what concerns us the most is the amount of space that is left when a loaded round is in the chamber. In an ideal world the cartridge will completely fill the chamber with no space but have no interference. This is not an ideal world so we have to have room for variations in ammo and dirt and powder fouling. We do this by having a minimum (go) and a maximum (no go) usually this range is .004 inch. We want to have no more space than a human hair so this is a job to be done with care and knowledge.

So why is this so important? Consider what happens when the cartridge is fired. Once the bolt is closed the firing pin hit’s the primer with sufficient force to crush the metal cover and ignite the explosive charge of the primer. This also pushes the loaded cartridge as far forward in the chamber as it can go and increases the space between the bolt face and the base of the cartridge to the maximum. Next the flash comes through the flash hole and ignites the powder. Pressure quickly builds and the thin brass walls of the case seal off and prevent any gasses from flowing towards the bolt. As the pressure quickly climbs it forces the head of case rearward stretching the thin sides of the case until the case head rest against the bolt face. If the distance is excessive the case head will be blown off and the full pressure of the cartridge will be loosed into the action. Remember the shooters eye is only a few inches behind this area and his hands and arms are lying parallel to the action. We are talking 50,000 lbs. plus with normal rifle loads. SCUBA tanks and welding cylinder have less than 3,000 so you get the idea.
But what if it just stretches the case but not enough to rupture? This is bad too especially for the reloader. This case is stretched thin just above the case head. When the reloader resizes he will push the shoulder back and the case will chamber again but the brass is already thin in this area just above the case head and when fired again the process repeats but maybe this time the thin area ruptures. If not this time maybe the third or fourth or sometime down the line. Also pushing that shoulder back each time usually shows up as a longer case neck needing to be trimmed and deburred.

All this shifting of the cartridge during firing also results in poor ignition of the powder and inconsistent accuracy as the bullet has a hard time getting started into the rifling straight. Misfires often result from the cartridge being pushed away from the firing pin.

But what happens if there is not enough room? Most firearms have built in safety mechanisms to prevent the gun from firing if the bolt is not fully locked in firing position. This is the scenario that insufficient headspace presents. The bolt face touches the case head before closing completely and when the trigger is pulled the shooter hears a click but it doesn’t fire. Many times a gun brought in for a new firing pin or a good cleaning when the real problem will be insufficient headspace.

So how do you measure headspace? The space to be measured is enclosed and out of sight so normal methods won’t work. Headspace gauges to the rescue. These are precision ground gauges that fit the area between the bolt face and whatever the cartridge comes to rest against. Most common are the family of rimless bottleneck cartridges. These include the 223, 308 and 3006 family of cartridges. Many times headspace gauges will work for a whole family of cartridges. The 3006 gauges will work for 2506, 270 Winchester, 8mm06, 35 Whelen, and 400 Whelen. 308 gauges handle 243 Winchester, 260 Remington, 7mm/08 and 358 Winchester. These cartridges and many others do not have a rim that projects outward past the case wall and rest on the bottleneck shoulder. The next type is the belted magnum. This type has a belt on the outside of the case just above the groove cut for the rim. This type headspaces like the rimmed case. The gauge measures only the distance from bolt face to rim. These types include 7mm Remington Mag, 300 Winchester, etc.

Next are the rimmed cases like 30-30, 303 British and 45-70. This gauge only measures rim thickness because that is what these cartridges rest upon even though some are bottleneck design. Last is the straight wall rimless that headspaces on the case mouth like 30 carbine and 45 ACP. Whatever the case type the gauges are used in the same way. First the chamber is cleaned of dirt or metal chips and then the go gauge is inserted. If the bolt will close without resistance the chamber is deep enough. Never try to force the bolt closed on the gauge because it is hardened steel and can damage chamber or bolt. Next remove the go and insert the no go gauge. This time when you try to close you should not be to close the bolt all the way. If you can, then the chamber is too deep for best performance. Next remove the no go and insert the field gauge and try to close. This gauge is usually .004 larger than the no go and if the bolt will close the gun is unsafe and should not be fired.

How can headspace problems be corrected? Too little headspace is the best problem. Usually a reamer turned by hand will remove a couple of thousandths and get us where we need to be. If more than a small adjustment the barrel should be removed and set up in the lathe to keep the reamer on line with the bore. For excessive headspace the barrel must be removed and the barrel shoulder set back towards the muzzle to allow the chamber to move closer to the bolt face. On an average barrel with 16 threads to the inch one full turn will send the chamber .0625 inch towards the bolt. Of course the barrel will need to be machined back maintain clearance and not touch the bolt face.

But what if the chamber is correct and the ammo is too short or long? Very important to understand that excessive headspace or insufficient headspace is a relationship of chamber size and ammo size. The same problems of an oversize chamber will be present when we have undersize ammo. In the last year I have seen two nice 7mm Remington Magnum rifles badly damaged when they were loaded and fired with 270 Winchester ammo. When the case expanded to fit the chamber it required more stretch that the brass could survive and the case ruptured. This amount of pressure blew out the magazine boxes and broke the floor plates turning them into projectiles that injured one shooters leg.

Headspace is critical for safety, functioning and accuracy. Make sure you measure everything several times and understand what you are measuring. This is not a “poke and hope job”.

 

 

 

“But that’s not why I bought it”

You probably bought a bore sighter when you first decided to start working on guns so you could sight in a rifle without shooting it at the range. You might have decided that it wasn’t worth what you paid for it when you fired that bore sighted rifle for the first time. If you were lucky or had a big target you might have been on the paper but certainly bore sighting isn’t sighting in.

Even though the bore sighter or collimator won’t sight in your rifle it is still a big help and an ammo saver. I always bore sight first and then fire a quick shot at 25 yards to make sure I don’t waste time getting on target. When I say quick shot I mean just an offhand shot. It won’t be perfect and it doesn’t have to be. Just remember where the crosshairs were on the target and make sure your shot is where you expect it. Remember if the scope is high above the bore the bullet strike will be low at 25 yards. As a matter of fact if you use a good ballistic program you can find out where your rifle will strike at 25 or 100 yards when it is sighted in at any distant yardage. This can be a real plus when you are headed to a 600 yard match and you have a new scope on your rifle. My 308 match rifle will strike 4.5 inches high at 25 yards when it is zeroed for 600 yard shooting.

Your bore sighter will also be used after you have finished firing  and have a good zero at a specific range. Say you just shot at 900 yards, it only takes a few seconds to record the bore sighter setting so next time you can confirm that you really have the rifle adjusted for 900 yards.

Now you probably already knew about bore sighters but maybe there are some other things that you can do with a collimator that hasn’t occurred to you yet. Here are a few of the neat tricks of the trade.

Checking scopes– use your bore sighter to look at the repeatability of your scope adjustments and backlash. Backlash is dead space when you are adjusting in one direction and you reverse. You are clicking right and the crosshairs are moving the correct amount each click but when you go back the other direction it clicks maybe 3 clicks before the crosshairs move. This drives good shooters up the wall in competition.

It goes something like this— You shoot and get a 10 but it is on the right side. You click one click left and shoot another 10 in the same spot. You put on another click trying to get to the X ring in the middle of the target but still hit in the same spot. Now you decide to try 2 or more clicks and get a 9 on the left side. Disgusted you move right one click and get another 9 in the same spot. If you knew you had this much backlash you would know how to adjust your scope. The bore sighter is the quickest way to find out about these internal problems in scopes.

Checking iron sights– the bore sighter will allow you to align iron sights just like a scope. It just might be a little harder to see! It can also be used to find out how high a new sight will need to be by using the bore sighter with a caliper. By holding the points of the caliper on the barrel where the front sight will go you can sight across the rear sight and adjust the caliper to center it on the bore sighter just like the caliper is a front sight. Of course it can be used the same way in place of the rear sight.  If you use the same bore sighter all the time you should know where on the grid will be closer to being sighted in!

You can even use the bore sighter to check bedding–If the crosshairs move when you slacken and tighten the action screws you might need to pay some attention to your bedding. If you can push the barrel from side to side in the barrel channel and the crosshairs stops in different locations on the bore sighter it will do the same when it shoots.

Being a gunsmith is hard enough. Might as well save yourself some trouble when you can. Learning to get the most out of your tools can make your life a lot easier!  Your tools will help you “Do Good Work” but they won’t do it for you!

 

Timothy P. Whealton

 

 

 

 

Springs

 

You probably took them for granted before starting a course of study in Gunsmithing. It’s easy to do, they are everywhere and cheap. They rarely fail compared to how much they are operated and are hidden from view. When you stop and think about it springs make a lot of thing possible that would be hard to live without. Before you can make one you have to know what a spring really is made of and how this little moving part works without moving parts.

Springs are made of carbon steel. The carbon has to be of sufficient quantities in the steel before the steel can be transformed into a spring. The best way to make sure of this is to purchase spring steel specifically for spring making. Brownells sells every type of spring making stock a gunsmith is likely to need and I’m sure there are others as well. The old blacksmith didn’t have a way to log on and order spring stock but you can be sure he would have loved to have the resources we have today. The old saying “they don’t make it like they use too” is true about steel and we should be happy. Steel quality was quite a headache for the old craftsman. Still there will be many times a small piece of steel left over from a job can be fashioned into a spring by a gunsmith if he has a basic knowledge that the old blacksmith learned through years at the grinder and anvil.

A quick way to find out if the steel has carbon in sufficient quantities for tempering is to grind a small section on the grinding wheel and observe the sparks. Grinding wheels cut out small cuts of steel so fast that the chips burn. If carbon is present the sparks will be more white than red, shorter than with low carbon steel and have a little flower bloom looking thing on the end. Try it yourself with a piece of cold rolled steel and a piece of spring and look at the difference. You will quickly get a feel for spotting the spring steel.

Ever wonder what the carbon does? Why it has to be heated? Why quenched? Well here is the short version as told to me by an old blacksmith. It might not be a good description for the chemist but it works for making springs and tools. The steel molecules are formed together in a matrix structure and the carbon is outside the matrix. The steel structures can slide past each other without the carbon being in the way. This happens when the steel is annealed or dead soft. When the material is heated to a cherry red heat the steel structures become very active and the matrix opens up enough to allow the carbon compounds to enter the matrix. Once the steel has the carbon dispersed throughout the matrix it is cooled rapidly. This can be a water plunge or other material that would give a little slower cooling than water. This might be quenching oil or even air. This will be important because some steel will form cracks if cooled too quickly. Now at this point in the process the steel is very, very hard. It will stand a lot of compression but no bending and will fracture with the slightest impact. Then the steel is heated a second time but this time the idea is to reverse some of the operation. This is called tempering or drawing. Actually drawing is a good name because your objective is to draw some of the carbon out of the matrix but not all. We want to leave enough so the steel structure will have some grab and resist moving and return to its former position when the pressure is released. This heat will be around 620 degrees F. Depending on the steel makeup. It can be done in a flame, on an electric element, in a heat treat oven or even in a lead pot. The temperature can be judged with color of the steel, oven thermostat, lead thermometer or temperature sensitive material painted on the spring. Quenching is not necessary but a lot of old timers liked to put it in dry lime or cold ashes (it insulates) and after the spring cools it can be tested with several compressions. You will know if you have a spring very quickly. Like I said it isn’t really what happens but it explained the process to me, maybe it will work for you. Or take a course in metallurgy and learn about austenite, pearlite and martensitic formations during heat treatment.

Springs will usually be preloaded (somewhat compressed) when installed in a firearm. Look carefully at the job the spring does before you try to “improve” how it works. Take the 1911 recoil spring for example. With the slide closed the spring is confined to 4 inches, at full recoil it is compressed further to 2 inches. Its job at full recoil is to have absorbed all the recoil, its job at rest is to close the slide and lock the barrel into the slide. If you cut a heavy spring it might still be strong at full recoil (2″) but too weak when the slide closes (4″).   I use a simple spring gauge to measure. A flat plate with a .250 hole is held in the vise. A long nail is inserted through the spring and the hole. The nail has a hole in the end that is hooked with a spring gauge and I can see how strong the spring is at 2″ and 4″. It also allows me to sort and tag all those springs that accumulate in the box.  I want my 1911 springs to have 6 pounds at 4″ and barely eject with the selected load for a target gun. Duty guns will be allowed to hit the ejector and eject with a snap to insure positive functioning.

Just remember if you cut a spring that you made it shorter but stiffer and more prone to breakage.

The Brownells catalog and most gunsmithing books have directions on making springs. After reading you can see it isn’t really technical, however nothing makes up for knowledge and careful work. So trying making a few practice springs before you make that special spring. Remember that spring will have your reputation on it when the customer pulls the hammer back on opening day!

Slings and mounts

 

 

While this job might not have the glamour of scope mounting it certainly holds the seed of disaster. I can’t count how many times I have seen a high quality firearm disfigured by off center sling mounts or beautiful wood split and damaged by a screw that was wedged into an improper hole. It reminds me of the golfer that has attempted the 60 foot putt with great care and deliberation but missed and then when the ball is 10 inches from the hole he casually walks up and taps to miss again! He thought the job was so simple that it didn’t need his full effort!

It looks like an easy job. The customer might even add to the illusion with terms like “just pop me a couple holes for a sling”. Might be more accurate if he said “I need two holes with a two step diameter drilled center on a curved sloping surface that has an easily damaged surface”. Bottom line is you won’t get any credit for doing a sling mount job perfect but you sure will catch a lot of grief when it is anything less! Luckily most guns come from the factory with some provisions for a sling these days but the occasional stock still turns up that will need to have sling swivels installed. Understanding the pitfalls of this underrated job might keep you out of a lot of trouble so learn these few tricks of the trade. It just might keep you from waking up nights screaming!

You can do this job with regular tools or save yourself some trouble and buy the specialty tools offered to the trade by some of the gunsmith supply businesses. Drills designed with two diameters that speed up the job will pay for their selves if you are running a full time business. In addition to the drills there are countersinks for the nut required on thin for end installations and drill guides that can help you center up the pilot hole. Brownells sells a tool that resembles a screwdriver. It has a pin that will engage the sling swivel hole and turn in the mounting screw allowing you to keep pressure on the screw to help it resist pulling out of the hole. These tools don’t make the job foolproof but they do speed up the time it takes to do a good job.

It will be the mount for the rear swivel that will cause the most problems. This is normally a simple threaded stud that screws into the stock a couple of inches from the toe. The mount for the forend is normally a 10/32 machine screw with a nut that has to be mounted in the wood below the surface inside the barrel channel to prevent disturbing the accuracy of the rifle. With the forend being relatively straight and flat it is simpler to layout the hole location on center. Examine the threaded portion of the rear stud and you will get a few clues as to what will be working against you. The threads start very abruptly unlike most wood screws. Normally a wood screw is designed to pull itself into soft wood without a pilot hole but one glance at this threaded shaft should be enough to let you know this task would be impossible on a gun stock with this type of threaded screw. This screw is designed to give maximum strength but will require a special pilot hole or it will pull up the wood around the threads before it pulls itself into the hole. This is hard to repair without going to drastic measures so plan ahead to minimize the risk.

The pilot hole is really the critical part of the whole job. It must be large enough to accommodate the shaft or main body of the screw but allow maximum wood for the threads to hold. I usually measure the minimum diameter of the screw with a dial caliper and use a drill only a few thousandths smaller to make sure it is tight but without danger of splitting the stock. If you don’t want to buy a special drill with a two step diameter you will need to drill a second step the diameter of the threads about 1/4 inch deep to prevent the wood pulling up as the leading thread pulls itself into the hole.

Finding the correct location for the rear swivel and making sure it is centered can be a little tricky. Brownell’s sells a neat little tool that is a piece of angle stock that has a drill bushing mounted through the center. In use it is simply pressed against the stock and held square while the hole is drilled. Lacking a drill jig you can hold the stock in a padded vise and level the stock front to rear. Next a center punch is used to mark the location for the hole. Something around 2.5-3 inches from the toe works best. Be alert to any special problems that might cause a problem like the working parts of an adjustable recoil pad or something similar. After the location is marked back up a couple of steps and give it a critical look. If all is well proceed to drill or correct it by moving over and center punching another mark. This is the value of marking the location, you can move it before it is too late! On very thin hollow stocks or synthetics it might require a machine screw and nut to secure.

The front swivel mount is normally a machine screw with nut because the slender forend will could split if the wood screw was wedged into a too tight hole. This mount will also receive the most stress since the gun is carried barrel up and if the sling is use for shooting the bulk of the stress will be on the front. It can also be located with the drill jig or easily centered with measuring using a dial caliper. This hole should be the size of the machine screw and allow it to pass through easily. The recess for the nut can be made with a mini grinder or a counter sink mounted on a drill. Don’t try to use a hand drill with a larger drill because drills are designed to pull themselves into the material and you will probably end up going too deep or pulling up surrounding wood. I like using a drop of thread locker to make sure it never comes out accidentally. This can be disaster since the gun is on the back and hard to grab when it pivots around and the muzzle strikes the floor. If your luck is like mine it won’t happen unless you’re on concrete!

It really doesn’t take that much longer to do a professional job and even though you won’t make a lot of profit it will be another of those crowning touches that make your work a little better than the norm. Do Good Work!

 

Timothy P. Whealton