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”.