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Rtheurer
Reply with quote  #1 
Getlemen

I have a weired scenerio. On my 6BR Im getting no pressure signs of anykind but am peircing primers every now and then. Its cratering on the others that do not peirce.

OK lets give you some background to work with here.
Equipment.
Remington 700 in R1 Tube gun stock converted to singleshot.
Dave Kiff oversized bolt coned and fluted and handle TIG welded
GTR firing pin, spring, and Shroud. ( standard pin, non light one)
Extreme CG M22 trigger.

I shot this rifle and barrel combo for 1200 rounds last winter and spring. took that barrel off and put on my 6MM superX barrel. shot that all summer. Just put on my old 6BR barrel and switched lots of Varget powder. All else being the exactly the same. My first thought was that I got a fast lot of Varget so Ive been backing off the load. The old load which I never ever had a problem and there was Zero signs of pressure is 30.1gr Varget. Norma Brass, CCI 450, and a Berger 105VLD. Shoots in the high 1's!!!!!
Now Im down to 29.8gr of this new lot of powder and Im still getting two pierced primers in 40 shots. Temp was 50-60degF
I have never seen Powder with that much varience before. Not that it cant be, but wow.
Im looking at my Bolt to make sure the firing pin hole is not damaged and causing the problem. These loads feed and extract with Zero effort. No ejector marks what so ever, and the edges of the primers are still round. except for a cup in the middle after firing. ANy way... the firing pin hole looks Sharp and clean that has No damage at all. Why all of a sudden am I having problems. I have a major event comming and now this......

before you ask.. no the firing pin looks nice and round with no burrs or sharp edges.

Dang it.

RussT
GerryM
Reply with quote  #2 
have the head space checked, You may be setting the shoulders back a tad too much. The case may be slamming back against the bolt. A wet chamber will sometimes do this also.
The load may not be the problem. If so there would be pressure signs. It is not unusual for Primers to flow back also. I had some F brand primers that were soft . They showed pressure signs and the load was safe. I switched to a primer with a harder cup and the problem went away.
I doubt there is anything wrong with the bolt.
Kiff makes the best.
I hope this points you in the right direction and that it
Helps you some,
Rtheurer
Reply with quote  #3 
Head space is good, I have my own Go and No go gages. I even went as far as putting some tape on the Go gage at the rim end found I have about .003 for head space. So the head space on the rifle is good to go.

I have a small Gage cut with my reamer to check my shoulder set back with the Harrel BR FL Die. Good there too.
Even if I was Im jambing the 105's in the lands.

So the mystery ( to me ) remains.

I loaded some ammo down to 29.5gr this is .6 less than my last set up with the other LOT # of powder.

RussT
infantrytrophy
Reply with quote  #4 
My experience with a new 6BR rifle was similar. I tried loads of 29.5 and 30.0 gr of RL-15 with 95gr SMK's and new Lapua brass, CCI BR4 primers. There was cratering of the primers, so after some advice on this board I sent the bolt off to have the firing pin hole bushed (and the firing pin turned down to a smaller diameter). The size of the new firing pin hole is about .009 to .010" smaller than the original.

Now there is no more cratering.

The gunsmith explained that the problem is the absolute size of the firing pin hole, not the fit of the firing pin in the hole. The theory is that the short 6BR cartridge ignites more quickly and impacts more abruptly on the bolt face compared to other cartridges.

I can't vouch for the truth of that theory, but I can say that there is no more cratering of the primers.

GerryM
Reply with quote  #5 

I see where this is going.
Yes bushing may cure the problem.
Some S actions {early needed this}
R,s also .
But i would try a harder primer first to make sure.
The other barrel has been fine, so i suspect the primer.
It would not be unusual for us to get some soft primer cups. BR 4 have a hard cup and also wolf SR Mags.
Rtheurer
Reply with quote  #6 

You would think that this custom PTG bolt would have a smaller than the typical Remington firing pin hole size. Of course this may not be the case here.

As far as Primers I was under the impresion that the CCI 450 Mag primers are amonst the hardest out there besides maybe the Milspec ones.

What really gets me is this is the exact same barrel as before. I just took it off for the summer and now reinstalled it. Rechecked the head space and started shooting it again.

I best call Mr Greg Tannel and see what he thinks.

RussT
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