12-06-2011, 06:41 AM
mac37 Wrote:I'll post some pictures tomorrow. If a bolt is out of battery, I thought it was not possible for the firing pin to reach the primer?
It might reach it, but it's not supposed to be able to strike deep enough to fire the primer. That's based on how far the bolt is rotated. The firing pin's forward motion is stopped by it's flange hitting the back of the carrier. When the bolt rotates fully into battery it allows the carrier to move forward far enough for a good strike on the primer.
If it's way out of battery the hammer and back of the bolt carrier are designed to keep the hammer from getting a good hit on the firing pin. If it's far enough out of battery, the hammer should not release. You might still get a very small primer dent by the momentum of the firing ping flying forward on closing, if it almost goes into battery.
Problems arise if you have several parts that are out of spec, or even in the corner of a spec, that combine in such a way as to allow an unsafe situation.
If the carrier is milled too deep for the firing pin, or the cam slot milled a little off, or the firing pin itself milled a little off, or somebody accidentally gives you one of those 7.62x39 firing pins that protrude a little farther, or the bolt lugs are milled a little off, or the lugs in the barrel extension are a little off, or the head space between the barrel and extension is a little off, or the shape of the hammer is a little off, you can get problems.
One or two of these things probably aren't going to cause a problem, but if you get several, maybe combined with a primer that is not quite seated far enough into a case, you can have a serious problem.
The AR design is very clever and they spent a lot of time designing them to be safe. They did a lot of analysis of failure modes like the ones listed above and tried to spec it out so that it would be safe with common manufacturing tolerances and with parts as they become worn.
These days, with everybody and his brother making parts, you don't have any guarantee they they are mil spec or to Grendel spec.
The first Grendel bolt I got was milled slightly off center. So the metal under the bolt lugs was slightly thinner on one side. The firing pin hit close enough to the center that it always fired, but a lug eventually failed.
The manufacturer did a very thorough job of testing the bolt after failure and determined that in addition to the off center milling, it had not been heat treated properly. I'm sure they had an interesting conversation with their supplier. There was no damage to the gun and I got a new bolt, but it can and does happen now and then.
Better to play it safe and get it checked out.
RR