punching holes in primers

[gadbmw]

info
Dpms lower, geissel trigger
308 24 inch upper w mickluk(sp?) break

I am currently shooting corbon 308 190g factory ammo, and it function fine.

I have been trying to find a reload for it with both 190 and 175 smk's. I have done ladder tests with the following powders, with the max book load being the top of the ladder and 1 grain drops for each level lower. lowest load tested 5 grains less than max. I have tried Varget, 4350, 4895, re15 and tac. With every powder as I reached the middle range of test loads I started punching holes in the primers, sometimes the primer circle material ended up in the bolt and jammed the gun. 4895 and tac had the fewest holes punched, and made it to the 4th "rung" in the test. All the tests were 2-300 fps under the corbon stuff. And no pressure signs on the cases, or primers that werent punched.

It was told to check the firing pin and firing pin hole diameter, and I took it to a gunsmith to measure it. He stated it was "ok". And called at a later time to ask if I measured the how far the firing pin extruded from the bolt, I need to take it back to let him use a better too than me using the wrong end of my calipers and doing math.... But from what I can measure its .050. I can find where ar15's are suppose to be .020 to .036, but ar10's may be different. I did notice my geissel is pounding my firing pin and mushrooming it out where the hammer hits it, not bad just barely an edge to it.

I need to reload for it, or I will have to sell it as I wont put out the cash for factory ammo.

The gun has 140 rounds of corbon 190's, 140 rounds of prvi 168 match and the ladder tests mentioned above down the tube.

Any help would be great, if there is another thread that addresses this please post it or pm me. I may not have used the correct words in my searches. I can also provide more info if it would help in you aiding me.
Thanks in advance
Greg

 

[SNAFU_]

Re: punching holes in primers

greg,
I had this problem with my 260 bolt gun....my gunsmith bushed and replaced the firing pin and solved the problem. Hope this helps

 

[SScott]

Re: punching holes in primers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gadbmw</div><div class="ubbcode-body">info
Dpms lower, geissel trigger
308 24 inch upper w mickluk(sp?) break

I am currently shooting corbon 308 190g factory ammo, and it function fine.

</div></div>

Have you tried different primers? CCI's are suppose to be tougher.
SScott

 

[salmonaxe]

Re: punching holes in primers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sunnyside Scott</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gadbmw</div><div class="ubbcode-body">info
Dpms lower, geissel trigger
308 24 inch upper w mickluk(sp?) break

I am currently shooting corbon 308 190g factory ammo, and it function fine.

</div></div>

Have you tried different primers? CCI's are suppose to be tougher.
SScott </div></div>

This has not been my experience... But of course my experience comes from using Small rifle primers in a rifle with a .308 bolt face and firing pin. CCI's standard #400's blanked the worst of all the ones I tried.

When it came to primer blanking, of the standard primers, Winchesters held up the best. BR and Match primers from CCI and Federal did no better than their standard counterpart. What DID work was magnum primers.

I could see CCI's #34 Military Primers potentially working better, since they are supposed to keep slamfires down. Most likely they have a thicker cup.

Here's something to consider. When I had the worst blanking, my firing pin had a really weak spring. Recently I changed it out and my cratering has gone down, and I have no blanking. Maybe your hammer spring is too weak?

 

[BCP]

Re: punching holes in primers

Try a different trigger? I seem to recall reports about geiselle triggers hitting a bit hard. If you have a stock trigger laying around that might be worth a try.

Could also try a harder primer but I haven't had pierced primers in any AR so I doubt it's that.

Here is another thread where a guy with a DPMS had it blow primers on him:

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1424884

I assume you are seating the primers far enough inside the case, properly resized, all that jazz.

 

[bsp212]

Re: punching holes in primers

I know someone that had the same problem with their LR308. I'll call them tomorrow and see what the solution was.

 

[steelcomp]

Re: punching holes in primers

Could be excessive head space, or an oversized firing pin hole. I think .028-.036 is what's recommended on F/P protrusion. Or could be soft primers.
How do the case shoulders look before/after firing?

 

[bsp212]

Re: punching holes in primers

OP, the person I was speaking of said they sent the rifle back to DPMS and it was returned with a new bolt and carrier group that solved the problem. He didn't know what the difference was.

 

[telcolineman]

Re: punching holes in primers

I am waiting for my AR 10 now, When I receive it I will measure the firing pin protrusion for you