Category: Basic Gunsmithing Skills

Revolvers

 

When I was a youngster just learning to work on guns the gun writers were spitting out articles proclaiming the end of the revolver. They said the informed gun owners of today would no longer accept the failings of revolvers when they could have a modern automatic. I think most of those writers are dead now but the revolver is as healthy as ever in spite of being over 160 years old!

It’s no wonder when you look at what the revolver has going for it. Safety is a primary reason many handgun owners pick a revolver. While you and I might live and breath guns and spend all our hours getting better acquainted with guns a lot of folks only want a gun for an emergency and feel more comfortable with a revolver. With no place for a cartridge to hide and built in safety features like hammer blocks the modern revolver coupled with the fact that a revolver will never cock itself many new gun owners are more confidant they can handle a revolver safely.

Another reason they select a revolver is simplicity. This is not a small thing to many owners. When you listen to the stories of people that have been involved in a real shooting it becomes apparent that simple is better. These people didn’t have time or thinking power to spare to find a safety latch, search for a magazine or pull back a slide. They needed a safe gun that they could put out and get into action with one hand. This simplicity is also on the mind of casual shooters and people that purchase a gun for someone else that might not be of a “mechanical mind”.

Really it doesn’t matter why they picked a revolver, it’s your job to repair,refinish or improve so you have to know how it works and the job each part plays in the functioning of the gun.

Here is how a revolver works. The cartridges are held in a cylinder that revolves as the gun is fired. Instead of cartridges being moved from the magazine to the chamber each cartridge has it’s own chamber. When you see how many malfunctions happen during the feeding cycle, extraction and ejection you realize making these manual operation that are done before and after firing can make revolvers very reliable and quick to get into operation ( especially if it is already loaded).

Like every thing else in life there are a few drawbacks for revolvers. The obvious is with several chambers and one barrel there has to alignment issues, reloading will be slow and all the parts that lock the cylinder in position and unlock it will have to be timed to work together perfectly.

When a revolver fires the cycle of operation goes something like this, the trigger is squeezed to the rear and as it moves the hand attached to the rear of the trigger pushes upward and contacts the cylinder to begin rotation. The front of the trigger pulls down on the locking bolt and unlocks the cylinder before the hand moves the cylinder. Now the cylinder starts to rotate to the next chamber. After it moves out of the locked position the cylinder lock slips off the trigger and a spring power it up where it slides against the cylinder until it rotates enough for the next locking notch to arrive and then the lock snaps into the locking notch. The hand that pushes the cylinder has slid off the notches in the rear of the cylinder as the lock slide into place in the bottom of the cylinder. While the trigger was moving rearward the back of the trigger was traveling upwards and pushing against the hammer cocking it rearward. When the cylinder reached the position where the hand pushed free, the lock snapped into place and the new cylinder was in alignment with the bore the hammer was rotated far enough back that it slid off the trigger and fired the cartridge.

This understanding of the timing of parts is crucial to revolver work. It is not enough that the part be the correct shape and work smoothly, it has to operate at exactly the right time. This timing is achieved by the part that operates or powers the part being operated. Most of the time the parts are rotating on a pin going through the action and small amounts of wear and damage close to the pin will result in large timing changes further away from the pin.

The best example of this might be the hand/ cylinder lock relationship. The hand is engaging the extractor very close to the cylinder pin and the cylinder lock notches are on the outside of the cylinder. Just a few thousandths stoned off the hand will keep the cylinder notches from alignment with the lock.

Revolvers are fascinating guns to work on. They require a through understanding of the cycle of operation and interdependence of working parts.

Extractors
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This small part gets a lot of blame for malfunctions. As a Gunsmith it will be your job to find the real cause of the problem and repair, replace or modify the part to cure the problem. Even if you replace the extractor with a new one a complete understanding of the part will help you tune and adjust the new part for best functioning.

The job of the extractor is more than meets the eye. Yes, true to its name it extracts the case from the chamber but it also has a role in the other cycles of the gun. When a firearm is used it will normally go through the cycles of loading, feeding, firing, extraction and ejection. Faulty extractors might prevent a loaded round from feeding smoothly or stop a bolt or slide from locking in battery (firing position). A careful study of the cycle of operation and knowing exactly when the extractor does its job will make you look smarter than a bird dog!

Control round feed or push feed? If the cartridge feeds up behind the claw of the extractor the action can be called a “control round feed” mechanism. Probably the most well known are the Mauser bolt actions and pre 1964 Winchester model 70 rifles but the term includes a lot more. Most semi auto pistols including 1911 style, most repeating shotguns and a lot of repeating rifle feed the base of the cartridge up behind the claw. If the extractor binds on the case rim as it slides in position then the bolt will jam and fail to feed. This might be from rough edges, a too strong extractor spring or the extractor jamming in its slot. Watching a dummy round slide into position might show the problem. If the action is a rimfire and you are testing with live ammo don’t forget that an extractor binding on the case can fire a rimfire cartridge when it dents the rim!

Push feed mechanisms like the Remington 700 and AR-15 will push the cartridge into the chamber until the cartridge stops and then the forward motion of the bolt will snap the extractor over the rim of the case. Broken, deformed and jammed extractors will not allow the bolt to travel forward enough to lock into position and can prevent the gun from firing. This might be obvious or it might be so slight that the bolt looks closed but internal locking mechanisms inside the bolt are not in proper position to allow the firing pin to strike the primer. These are safety mechanisms that prevent firing without the bolt being in battery ( in battery is a term to describe bolt locked into safe firing position). Many times the shooter is convinced the problem is a broken firing pin because the action snaps but there is no mark on the primer.

Extractor geometry has a lot to do with how well it functions. The fired case has to rotate around the tip of the extractor to get out of the gun. If the body of the extractor is in the way the shell rim will be pried out and the shell left in the loading port (smokestack jam). If the extractor is thinned out too much it will break. Usually the factory engineers have worked out the dimensions but frequently with aftermarket parts a little touch-up can help.

Work carefully and understand the job before you start and always “Do Good Work”.

 

Testing Firearms Safely

 

Only a truly foolish person would test fire anything from the shoulder if there any indication that this firearm has a problem that might result in a catastrophic failure (BLOW-UP!). Only after a through inspection that reveals no damage to critical areas of the gun and an exhaustive inspection of the ammunition is it time to test fire. This inspection should pay special attention to the high pressure areas of the gun and be done in sunlight or strong artificial light. The receiver, bolt, chamber area barrel and stock should show no sign of impending failure such as cracks, bulges or stretching. If you stop to consider the normal working pressure and failure pressure in a modern firearm it makes it clear why these precautions are necessary.

Many times the firing history of a particular firearm will alert you to a possible problem. If the customer brings it to you because it blew the head off the case last time it fired then you know something wasn’t right. Maybe it was the wrong ammo, or maybe a reload with insufficient headspace, or maybe it has been rechambered to another cartridge or just bad brass or any of another dozen causes but if it happened last time it is up to you to find out why so it won’t happen again. Listen carefully and ask questions to make sure you gather as much info as possible from the owner.

The ammo is always suspect in any blow-up. Ask if it was reloaded ammo. If it was reloaded then by whom and what was the load? Was the gun fired before the blow-up? Did that round sound normal and was there an impact from it? Has this happened before? Do you have any ammo from the same batch? If the fired case is available for inspection look closely for signs of high pressure such as brass flow in the unsupported areas of the bolt head like the ejector or extractor. Look at any fired brass from the same batch of ammo for signs of high pressure as well. Primers flattened on the edge might indicate that this load was too hot for this particular gun. If the entire head is blown off make sure the ammo was not resized too much leaving excessive headspace when it was chambered. This test can be done using a case micrometer or comparing the reloaded cartridge with a known factory round. If it is a wildcat and no ammo exist for comparison remove the firing mechanism for safety and load a round into the chamber with a shim over the bolt head. If the bolt will close with a .010 inch shim between bolt and cartridge head the gun should not be fired. Carefully pull the bullet and weigh the powder and bullet to make sure it wasn’t a hand loading mistake. Inspect the powder charge and compare with a known sample to make sure powder didn’t get dumped out of the wrong canister. When you are finished inspecting ammo you can move on to the firearm.

Even if you are sure the ammo caused the problem the firearm will still need a detail inspection to make sure it was not damaged by the faulty ammunition. Test headspace in the usual way with the correct headspace gauges. Make sure the chamber has not been damaged so the hardened steel headspace gauges can rest upon the correct surface in the chamber. Looking closely at the outside of the barrel will usually show if there are any bulges. Many times the bulge will be slight but by looking down the barrel when the gun is shouldered the reflections of light along the outside of the barrel will show an abnormality that might otherwise go undetected. After the barrel is cleaned a tightly fitted patch saturated with oil will allow you to feel if there an area of less resistance when you push it through the bore that might indicate an enlarged area.

If there is any doubt about the caliber or the firearm is not marked you may want to do a chamber cast. It can be done with lead but Brownells sells cerrosafe that is 10 times easier to use and safer than lead due to the working temp being less than 200 degrees compared to 600 degrees for the lead. Follow the instructions for the best results but it really isn’t much more than you plug the bore ahead of the throat with steel wool and pour the molten cerrosafe till the chamber is full. Tap it out after it hardens and you have a perfect reproduction of the chamber and throat. It should be a little larger than the ammo if you are comparing the two side by side. Remember the ammo has to go inside the chamber. This is also a good way to look at the throat length and concentricity. The rifling should start evenly around the bullet and the casting will show this. This is incredibly important for accuracy. Save the casting and show the owner if you discover anything wrong like a damaged throat. The cerrosafe is reusable for years.

The receiver has to withstand the pressure of firing and must be inspected with a critical eye for any sign of failure. Be especially careful when looking for cracks or damage in the load bearing area between the barrel threads and the surface that the bolt lugs rest upon. If the bolt is a rear locking type this means virtually the entire receiver. If the firearm is of a case hardened manufacture look closely at these areas for signs that the bolt lugs are setting back into the receiver. This is seen on Mauser bolt actions that have been have the bolts lapped for better contact. The lapping cuts away the hard skin and exposes the low carbon steel to the high pressure of the bolt lugs during firing. It might also be a problem on a receiver that was burned in a fire. The fire annealed the steel and the receiver was later polished and reblued with the new owner thinking he got a great deal.

Having a perfect receiver doesn’t help much if the bolt is damaged. After it is cleaned look it over carefully with a strong light. I found that if you don’t have anything else you can wet the clean area with a high lighter pen and wipe with a dry cloth. Then go in the closet and find that black light from the party at your house in the 70’s. You might want to repeat the test a few times to make sure it isn’t just a tool mark but if any doubt exist consider it bad and destroy it or send it too the factory for replacement. Of course if it is a 1898 Mauser that might be a problem too. All those B-17s didn’t leave much of a factory but luckily they were made in enough numbers to have a lot of parts left over! Never leave a bolt with possible damage in the parts bin. It would be a recipe for disaster!

Only after the ammo and firearm have been completely inspected are you ready to test fire. This is a test firing to expose what went wrong when the gun-ammo combination failed. Test firing a firearm that jams is called function firing and has no expected risk of danger or shrapnel. Our goal is to fire the gun without exposing the tester to harm and then inspect the fired case and firearm for any damage or dimensional changes that indicate a problem.

While you could build a fixture to hold the firearm it can be done safely with nothing more than an old tire and some rope. Place a pad of some type like an old towel under the front and place the butt inside the tire so it will have something firm to take the recoil. Next use a soft rope and tie down the front to the tire. If you are using a chronograph or target it would be positioned it front of the muzzle at this time. After making sure the firing and target area is safe tie a loop in a small cord looping it through the trigger and extend it back to a safe area. Test by dry firing and make sure it snaps. Make sure you have eye and ear protection and everybody is viewing from a safe place. Finally load and place some type of cover over the gun like a piece of old carpet. Move carefully to the safe area without tripping on the cord and shout “fire in the hole” (optional) before pulling the cord.

After firing begin the inspection process anew looking at the fired case and the firearm for any signs of failure. Hopefully you will find all is fine and firearm can then be function fired or accuracy tested.

While this might seem like a lot of trouble it really is not much effort and doesn’t take much time to do safely. Even if you never have one come apart it is still better to be safe.