.308 Brass Not Extracting
Some folks are having trouble with brass not extracting, sticking in chambers, etc. Most of the problems involve reloaded ammo so I’m going to talk about some basics. Two things come to mind when loading for a gas operated rifle like the M14. First, use a small base sizing die. I know many folks don’t have trouble when using a standard die, but a small base die will insure every round feeds smoothly into the chamber. When a round is fired, the case expands to fill and tightly seal the chamber. After the gas pressure drops the case normally shrinks slightly, allowing easy extraction. At least that’s how it is supposed to work. Sizing with a small base die will insure that case shrinks a little more and extracts easier.
The M14 is very hard on brass. It has a lot to do with cycle timing, chamber size, and the internal effects of gas pressure. Generally, 7.62 mm chambers found in the M14 are generous while .308 chambers tend to be tighter. Tighter chambers work fine in bolt action rifles, but can cause problems in a gas operated rifle which tends to start extraction early in it’s timing cycle, gas pressure is often still present when the bolt starts to withdraw. The result is stickier extraction, brass flow (brass actually flows toward the neck of the cartridge case), and case stretching. This is the reason that brass fired in the M14 only lasts about 3 to 4 loadings before cases start separating about ½ inch above the base. So don’t expect long life and several reloads from your brass.
Brass flow into the neck isn’t much of a factor in the M14 since the brass cannot be fired enough times to result in significant increases in wall thickness. The serious problem is case stretching. From the first firing, 7.62 and .308 brass stretches a lot. The brass must be trimmed after the first firing. I have found that trimming 5 to 10 thousands short will allow reloading without further trimming for the remaining few reloading cycles. It’s guaranteed that not trimming your brass will result in cases that stick in the chamber and develop excessive pressures.
The factory length for .308 brass is 2.015”. I’d recommend trimming to 2.005” + .005” max.
By Ted Brown
Shooters Den
NOTE: Please read all necessary safety information and specs before reloading any ammo. Information regarding this commentary is just that. Reload ammo at your own risk. This online blog/journal and Mr Ted Brown is not responsible for any mishaps that may occur to you and your rifle.
Best Regards,
M1A96819
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