Pierced Primers - Excessive Headspace?

[W.E.G.]

That is my understanding too.

I have always puzzled about WHY do they bother to offer the CCI #41 if it is, in all respects, IDENTICAL to the CCI 450.

 

[Jim K]

I repeat what I said before. Either the hammer spring is weak or the firing pin is too light. But I will say that thin primers can make the problem worse.

Note that the "standard" primers show extrusion back into the firing pin hole. If you disassemble the bolt after getting those "pierced" primers, you will find small pieces of brass in the firing pin channel from the primers that were "pierced". Switching to the harder/thicker primers solved the problem because they will better resist the internal pressure. But note that ring around the firing pin dent; the primer is still trying to get around the firing pin, indicating either high pressure or a weak firing pin blow or both.

The firing pin is not "punching holes" in the primer, the internal pressure is doing that.

Jim

 

[W.E.G.]

The ring was in part a function of the fact that the boltface around the firing pin orifice was greatly eroded from the hot gases. I don't still have that bolt. Threw it away years ago. The brass in my pic is brass I fired in 1997. Been sitting in a bucket until yesterday. Figured I'd snap a few pics before all the evidence was destroyed.

I went through several hundred pierced primers, several ruined bolts, and several ruined firing pins, in that gun before switching primers.

Yes, there was a lot of primer metal discovered in the mechanism after a day at the range.

I suppose we can debate until we are blue-in-the-face over whether the hammer spring is too weak.

In my opinion, the load was quite hot (run my numbers through Quickload - you will see), and the thin primer metal was the weak link. I could have had the hammer spring of THOR, and I'm quite certain the result would have been the same. Many other of my teammates at the time were using the same, or similar loads, in rifles with different triggers.

In each instance - same result - until we all figured out that we needed to use magnum primers to end the problems we were causing.

Remember too, 1997 was right about the time the mouseguns were overtaking the M14 in service rifle honors. We all thought we had to hot-load (overload?) .223 ammo to be competitive. I have since learned that ragged-edge loads are not generally necessary to achieve success in high power rifle competition.

 

[Jim K]

Well, if the firing pin hole is oversize, primer metal can extrude back around the firing pin regardless of the firing pin momentum. And that also can hang up the gun as at some point, those bits of brass build up and stop the firing pin. Of course, the firing pin hole is probably oversize due to pierced primers resulting from a weak hammer spring or a light hammer, so the thing is circular.

Jim