Firing pin hole size

[Rtheurer]

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]

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]

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

 

[gaintwist]

I can't imagine why you suddenly have this issue. A chrono reference of old/new loads would help but here is a similar primer issue I had with my Dasher that was solved simply by using harder primers. SRMags in my case. I switched from the usual Russian SRM's to the Rem 7.5 for a test and didn't get off 4 shots before I had to abandon that primer. Back to SRM's and no problem. My action was a Nesika J. My Nesika J in 223 really had a rough life in the primer area and I had it bushed by Greg T. and that cured all its piercing probs. You might measure your pin and email Greg to see if he can help you. He was quick and inexpensive in my experience. www.gretanrifles.com

 

[medicineman]

The problem could be in your trigger. I've experienced the same dilemma with a Rifle Basics trigger. Sometimes it would fire fine, sometimes it would misfire and other times it would blank primers. The trigger would drag against the striker assembly, slowing the pin fall and sometimes restricting the travel. This causes non support of the primer where the pin tip contacts. I changed the trigger back to factory version and the problems disappeared.

 

[ericskennard]

I have seen this time and time again. Usually with those that switch barrels but more often those loading 6mmBR to the max. It all seems to happen around 800 to 1200 rounds.

Your barrel is super dirty and probably has a carbon ring right at the lands and grooves. I know, I know, You clean the barrel until the patches are clean. I don't doubt it. But you must check the bore with a bore scope. It will scare you.

Get some JB bore cleaner or Iosso paste and scrub the chamber and the first 10" of the barrel like a crazed maniac. You will be shocked at the difference it can make. If it doesn't, I will give you $25 for the barrel!

The firing pin is a good suggestion. Have Greg install a bushing and a small diameter pin. That will help tons. He has a very fast turn around on jobs like this.

ERIC

 

[Rtheurer]

Eric

You hit the nail on the head. I own a Bore scope and have for 5 years now. There was alot of Carbon build up this time. I scrubbed it clean as wistle ( you can do this if you have scope) and went back to the range.
The problem was compounded by the New Lot of Varget that is alot faster than my previous lot was. I had to drop the charge back .6 of a grain to get the Velocity back down to the 2830fps that the rifle likes. This after Chronographing and actuall seeing what was going on.

After the big matches planned for this fall Ill send the bolt to Gregg to get it bushed. Kinda peaved that I have to do this on a costom Bolt.

Eric you couldnt pry this barrel out of my hands right now. This barrel holds 9 current National records, its a goodin.

So the moral of the story.
1. Have access to a bore scope. For cleaning.
2. Never trust one lot of powder to the next
3. Dont assume clearance for firing pin is perfect.


Thanks Eric... You may have helped more than one person with this post.


RussT

 

[forsyth793]

Hey Russ,
My Kiff Bolt has a .076 Firing Pin Hole, do you know the size yours was?

Spike