Q: I’m having problems with my .308, which has the primers backing out of my reloads. My load is 43gn of AR2206H behind a Hornady 150gn Interlock bullet.
Can you tell me why this is happening? What can I do to fix the problem?
Hal Beeson
A: In my experience, there are basically two factors interacting that cause primers to back out of the case.
The usual cause is excessive headspace. In this instance I’m not talking about nominal headspace of the rifle’s chamber/bolt fit; I’m referring to the relationship of the unfired case to chamber and bolt. Excessive headspace is commonly caused by the handloader when the case is sized too much and the shoulder is set back.
When the firing pin falls, the case is driven forward as far as the chamber or the extractor will allow just prior to ignition. The case mouth, the thinnest part of the case, then expands to grip the chamber walls and the primer is pushed out by pressure coming through the flash hole.
If the load is a standard one (around 50,000-55,000psi), the base of the case is then rammed back against the bolt face, stretching in the area just forward of the web. This generally rivets the primer over, giving it a very flattened appearance, which often leads the handloader to think that the load is too hot. The reality is, however, that it is caused by an excessive headspace situation and not a hot load.
If, however, the load is mild and the case is strong, there might not be enough pressure to stretch the case. In this instance, the primer is left protruding. The load you are using is an extremely mild one for the .308 — actually a reduced load. You can solve this by increasing the charge by three grains.
To correct the problem, it is necessary to hold the case firm against the bolt face. You can do this by seating the bullet out so far it is jammed tight against the lands when the round is chambered to prevent the firing pin driving the case forward. Firing the round in this situation causes the thinner portion of the neck and shoulder to fill out the chamber, with the base of the case tight against the bolt face, so that it doesn’t stretch toward the base of the case, thus weakening it.
Once the case has been expanded in this way, it can be reloaded in the normal way with normal bullet seating depth, but you should pay attention during the sizing operation so that you don’t set the shoulder back again. To do this, back out the sizing die so that it isn’t touching the shell holder. All you need to do is size most of the case neck.
Then if you increase the charge, it should solve the problem of primers backing out of their pockets.
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