Pierced Primers

[DickDavis]

I don't know whether to post this here or in the reloading section but here goes....
I have an AR10 that has been rebarreled to .260 Rem, w/ a Lilja 1:8 twist 24 in. barrel.
I am loading 139gr. Lapua Scenar under 39.5 thru 43.5 gr. of H4350, w/CCI BR2 primers in new Lapua cases.
All loads exhibit raised primers in the location of the firing pin hole. The primers do not appear to be excessively flattened, just raised like they are trying to flow into the firing pin hole.

The above loads are producing the following velocities:

39.5=2536fps
40.0=2537
40.5=2584
41.0=2613
41.5=2595
42.0=2670
42.5=2720
43.0=2728
43.5=2757

The 43.0 and 43.5 loads have pierced primers and the recoil is substantial!

I have asked some of my fellow shooters for comments and so far they have said to try H4831sc and/or an adjustable gas block.

The gun has the Tubbs CS recoil spring and heavy carrier weight system.
I have only shot one round without the carrier weights, the last one I had, (43.5gr.) and still got a pierced primer.

I am halting any further work on my reloads until I can resolve the problem.

Any recommendations would be greatly appreciated.

Thanks

 

[DavidAR10]

Re: Pierced Primers

Hi guy,

http://demigodllc.com/articles/the-case-for-260-remington/?p=3

 

[DickDavis]

Re: Pierced Primers

Thanks, David...I read the article...excellent info, but it doesn't help me to solve my particular problem.
I did find it interesting that his go to load was only 40.7 gr. of H4350, less than Hodgens recommended starting load of 41.5!

 

[culater]

Re: Pierced Primers

Every gun is different and should go by what the gun is telling you.back down on the powder and shoot 5 shot groups. Just find the sweet spot and deal with the speed.

 

[trisurvivor]

Re: Pierced Primers

Stupid thought, but I can say the same thing inmy reloads in my pof p308. I am nowhere near top end. I switched from 210m's to br2's.

Are we sure it is not the lapua brass? I have never used it prior to my 308. It seems much stiffer like steal cases. Which would lead me to believe the primer will get more pressure on it to cause this. The primers are not flat as I have done enough reloading to know this. Something is different, and the brass is the only thing different.

Thoughts?

 

[match308]

Re: Pierced Primers

The port in your bolt face is too large. I had the same issue and POF changed the bolt out. She runs like a scalded ape now.

 

[RyeDaddy]

Re: Pierced Primers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TBannister</div><div class="ubbcode-body">The port in your bolt face is too large. I had the same issue and POF changed the bolt out. She runs like a scalded ape now.</div></div>

I would agree with this, my POF gives massive primer craters at anything above starting loads, but the velocities and brass and primer edges all show loads to be safe. I only "pierced" one primer and that was slightly above book max, so I consoder it a non-issue for me, I just keep within book max and discount the craters. My Rem 700's all did the same thing.

Never thought to call POF about it, maybe I will.

 

[DavidAR10]

Re: Pierced Primers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 7.62NATO</div><div class="ubbcode-body">Thanks, David...I read the article...excellent info, but it doesn't help me to solve my particular problem.
I did find it interesting that his go to load was only 40.7 gr. of H4350, less than Hodgens recommended starting load of 41.5!</div></div>

I'm a Dapper Dan man [ARMALITE]... don't want no Fop. And, I'm going 6.5CM on my oldest of three (3) ARMALITE AR-10s.

I was thinking that you might be too hot in your load after reading pg.3 but it looks like an over-bored firing pin channel.

Get that proper bolt and it looks like you'll be able to burn that barrel out faster than we both thought.

Best to you.

EDIT: Don't forget the new firing pins, sir.

Yeah, I really do think that you're running too hot.

 

[FLIGHT762]

Re: Pierced Primers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DavidAR10</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 7.62NATO</div><div class="ubbcode-body">Thanks, David...I read the article...excellent info, but it doesn't help me to solve my particular problem.
I did find it interesting that his go to load was only 40.7 gr. of H4350, less than Hodgens recommended starting load of 41.5!</div></div>

I'm a Dapper Dan man [ARMALITE]... don't want no Fop. And, I'm going 6.5CM on my oldest of three (3) ARMALITE AR-10s.

I was thinking that you might be too hot in your load after reading pg.3 but it looks like an over-bored firing pin channel.

Get that proper bolt and it looks like you'll be able to burn that barrel out faster than we both thought.

Best to you.

EDIT: Don't forget the new firing pins, sir.

Yeah, I really do think that you're running too hot. </div></div>

I agree an oversized firing pin hole in the bolt may be the issue. The firing pin hole shouldn't be larger than .065", if it is, it can cause a cookie cutter effect.

The hole should be between .058"-.060".

If your pin hole is within spec., you might be overloaded. An adjustable gas block might work well in that caliber.

I shoot an SR-25 in 308 Win. and have been plagued with the rifle beating brass badly. I've put in a Tubbs CWS and his buffer spring. It has helped a little.

 

[DickDavis]

Re: Pierced Primers

Based on the suggestions you have given me I removed the bolt that was supplied w/the 260 barrel and compared it w/3 of my Armalite AR10 bolts and the firing pin hole in the 260 bolt is significanly larger than the Armalites.

I have now way to measure the exact FP hole diameters, but I can see the difference in the diameters with my naked eye.

I have a call in to the fellow that built the upper to find out why the difference in FP hole sizes and who manufactured the bolt. When the bolt is in battery, I cannot pull it back with just my hands, I have to use a plastic hammer to tap it back! And this is without a round in the chamber.

Until he returns my call I am going to load some more rounds using the H4350 and try them using the Armalite bolt. Altho the Armalite bolts are for a .308, I don't think that should create a safety problem.

If the situation persists, I have a JP adjustable gas block that I will try next.

I will continue w/this thread until I find a solution, for those enquiring minds who want to know.

 

[hlee]

Re: Pierced Primers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 7.62NATO</div><div class="ubbcode-body">When the bolt is in battery, I cannot pull it back with just my hands, I have to use a plastic hammer to tap it back! And this is without a round in the chamber.
</div></div>

This sounds like a significant problem... You cannot pull the bolt open with the charging handle? I am having a hard time with what the above means. Do you mean that if you just have the bolt carrier and bolt, you are unable to move the bolt "out" without a hammer? Call me crazy, but this sounds like a problem.

 

[GGGN]

Re: Pierced Primers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DavidAR10</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 7.62NATO</div><div class="ubbcode-body">Thanks, David...I read the article...excellent info, but it doesn't help me to solve my particular problem.
I did find it interesting that his go to load was only 40.7 gr. of H4350, less than Hodgens recommended starting load of 41.5!</div></div>

I'm a Dapper Dan man [ARMALITE]... don't want no Fop. And, I'm going 6.5CM on my oldest of three (3) ARMALITE AR-10s.

I was thinking that you might be too hot in your load after reading pg.3 but it looks like an over-bored firing pin channel.

Get that proper bolt and it looks like you'll be able to burn that barrel out faster than we both thought.

Best to you.

EDIT: Don't forget the new firing pins, sir.

Yeah, I really do think that you're running too hot. </div></div>


Who sells bolts with a small hole I need a couple of them. DPMS pattern.