Punctured Primers

[SMLE]

Hi Folks,

I’ve either been a bit thick or I have a firing pin defect I think, any thoughts appreciated before I pop off to a gunsmiths at the weekend.

6.5 creedmoor loaded with 35.9 grains of N150 under 139 scenars (max in load table is 35.5). This has proven a great load for last 400 or so rounds giving me about 2670fps. and good grouping about 0.75 moa at 600 yards. Using CCI small rifle 400 primers - all I had available at the time but worked great.

Absolutely no pressure signs at all across 400 rounds or so. I was confident in the load and took it out to 1000 yards a few weeks ago with similarly good results. Again, no pressure signs at all.

Loaded up a new batch of rounds last week for a 1000yard Bisley session yesterday. This time loading with a Redding bushing die to give 2 thou neck tension in two batches, some previously full length sized four times and some once fired virgin brass neck sized on this their second load. New tub of N150 used. Everything else the same.

Every shot yesterday produced either a punctured primer or cratered primer with extractor marks. I stopped shooting them after a few shots and also noted evidence of gas impact on magazine follower.

Not able to figure it out, I tried a couple of rounds of my friends 6.5 creedmoor he was using and both of those rounds had punctured primers too, no evidence of this when fired in his rifle by the way.

Recognising I introduced two new variables here, the new powder batch and neck sizing rather than full length, what are people’s thoughts? I would not expect to see significant pressure differences between batches of the same powder that go from ok to catastrophic at least!  Would neck sizing make such a difference? The bullets seated with no cause for concern in press “feel”. Or, is this a hardware issue?

Any thoughts gratefully received before I speak to a gunsmith to check my rifle and bolt over. I’d just like to understand this if I can.

[Ronin]

Don’t know what rifle your shooting but unless the weapon has a adjustable firing pin assembly (that’s worked loose) it’s unlikely  to be the gun.

 

your load is slightly over on recommended safe max

Thats could be the issue 

 

You may also have a carbon ring at the throat causing increased pressure 

Neck sizing is “old news” if always recommend full length Re size for consistency

What are the loads like when f l resized ?

 

Your pals rifle / load may not like yours regardless so I wouldn’t draw any conclusions from shooting your cartridges in his gun (chamber and tolerances likely to be different ) 

 

[dully1963]

Just to add my thoughts the new tub of powder is hotter than your last tub , if you have any of the old tub left try a couple of rounds with that powder just to check. plus I would think a creedmoor would be better on bench rest  primers

 

[Popsbengo]

What was the weather like?  Was it much different from any previous shooting of that load combination?

[bradders]

Multiple piercings.....your firing pin is knackered

[Catch-22]

My previous rifle (Tikka 595 in 6.5x47) developed some issues around the 500 round mark with piercing primers all of a sudden.

The cause was the large firing pin having issues with the small rifle primers. Bushing the pin resolved the issue. 

[GeorgeB]

Agree with Bradders - your firing pin will have been damaged by the white-hot gas plasma from the pierced primers. The problem is due to using CCI 400 primers which have thin cups. I would avoid using these in anything beyond.22 Hornet! 

CCI 450, CCI BR4, and Remington 7 1/2 BR  all have thicker cups, there may be others which are also OK.

[SMLE]

Thanks everyone for responding.

My rifle is now with Norman Clark for a once over and check before/if I use it again.

I’m beginning to accept the inevitable and admit that the root cause is me. I agree, the primer choice was a poor one, but I had them to hand and they appeared to work so I thought why not stick with them. Wish I hadn’t to be honest as I suspect a slight lift in “jip” with a new powder tub was enough to break the camels back and cause the failure. Hopefully there’s no gas damage to pin and bolt, and I suspect Norman will happily empty my wallet if there is, but he seemed quite hopeful that all would be fine this morning when presented with the rifle by a bashful yours truly.

So, assuming I get the rifle back, on to more load development, everyone seems keen on RS60 or 62, so think I’ll start there..... BR4 primers this time though...!

 

[VarmLR]

As above....thin primers + pierced primers = gas cutting of firing pin (and bolt face) which exacerbates the issue and means increased risk of same on all future firings.  I learned this the hard way and with .223 and 6.5CM you need to consider the use of magnum primers with a cup thickness some 5 thou thicker than standard primers to avoid this issue.  Hope you get your rifle back soon with the issue resolved and sort a revised reload recipe.

I can heartily recommend RS62 and Murom KVB-M primers or CCI 450 for LR or KVB-223M and CCI 250 for SRP brass.  Come to think of it, I think better results were had a few years back with Remmy 7.5 primers in SRP brass (may still have some knocking about in supplies now I've reminded myself!  Obviously Remmy 9.5 for LRP).  Remmy ones are considerably hotter than the KVB or CCI magnum/BR versions from memory.

[Chris-NZ]

Might have ya CCI numbers about face there Varm?  😉

[SMLE]

Cheers Varm, been reviewing quite a bit of info on here about load development for the 6.5CM, some from you, so thanks again and don’t worry, I know the number assignments for the primers.