Firing Pin Bumping Shoulder?

[Florida Wally]

new brass start over, maybe, maybe not

I’m pretty sure the brass and my annealing process is fine. Just a bad primer.

 

[Florida Wally]

Try just chambering a case no dry fire then measure

I did that when I first resized the case. Bolt closes with no resistance with a 0.001” bump on a fired case.

 

[rijndael]

I did that when I first resized the case. Bolt closes with no resistance with a 0.001” bump on a fired case.

FWIW: With all of my guns I can feel resistance with only .001" of shoulder bump.

 

[BoydAllen]

In the area of cast bullet rifle shooting, it has been known for a long time that repeated low pressure loads will shorten the "headspace" of a case. This is easy to test. I have.
Added a little later: I should have mentioned with rimless cases. Obviously with a belt or rim this would not be an issue, assuming close fit on the rim or belt. The Swift is a special case, although it is semi-rimmed the rim is not commonly used for headspace.

 

[Florida Wally]

FWIW: With all of my guns I can feel resistance with only .001" of shoulder bump.

That has been my experience as well. I usually end up bumping 0.002”. This particular brass has only been fired once, so it probably hasn’t yet completely fire formed and will likely need 0.0015” to 0.0025”.

 

[big5ifty]

I did that when I first resized the case. Bolt closes with no resistance with a 0.001” bump on a fired case.

This means your headspace is not correct, more so if you still have the firing pin in the bolt.

There has to be some resistance in the last inch of bolt travel, with the firing pin removed from the bolt.

If you have no resistance with the firing pin removed, it means the bolt falls closed under it's own weight.

 

[6BRA]

My experience with OCD 6BRA.They were headspaced excessively compared to Lapua 6 BR. .004 crush headspace fireforms Lapua easily without jam. OCD 6 BRA Was bumped .009 from fireformed Lapua 6 BRA. Then they tell you it only woks with Legacy reamers. Stick your brass where the Sun doesn't shine. I will never own anymore Alpha. You also have primer pockets on OCD that are beyond tight. As several have stated if you have no means of measuring crush, the primer probably wasn't seated deep enough. As far as over annealing, I don't see that being the cause. I have dual torched brass accidentally at 8 seconds 1/4 inch below the shoulders glowing red. Fired it. It wasn't dead soft...I can't imagine a firing pin ever bumping a shoulder. My advice find a different brass or uniform the OCD pockets.
If your primer was sticking proud..the firing pin strike drove the primer in and your headspace shoulder bump was never measured right as the primer was proud

 

[Florida Wally]

Thanks everyone for your comments. I went out to the range yesterday after reloading the case I had the issue with and it fired fine. Same lot of primers, same lot of powder. I also fired the other cases that I used to experiment with and all of them fired fine. In addition, I fired 20 more of the cases with the pink necks and they fired fine. The “over annealed soft shoulder” theory has been debunked in my mind. My problem was most likely due to a poorly seated or bad primer. As most of you posted, it is pretty difficult to over anneal brass. I’m still not sure about what the pink color is, but it doesn’t affect bullet seating or results on the target. The cases that I dry fired and the original case that didn’t fire, all had a base to shoulder measurement about 0.001” to 0.002” less than the my other fired cases. I am thinking these will fire form during the next firing.

Interestingly, I have found that if a case is primed with a live or spent primer, and not loaded with powder or a bullet, when fired, the force of the firing pin will bump the shoulder. If it is fired again, the shoulder will bump more. I was able to bump the shoulders back an additional 0.005” - 0.006” on some cases.

 

[6BRA]

What tool are you measuring shoulder bump with?

 

[Florida Wally]

I’m using the RCBS Precision Mic headspace gauge.

 

[Coyotefurharvester]

If I use lemi shine and drop of dawn/vinegar in either my tumbler or ultrasonic cleaner the necks will be pinkish. Annealing doesn't alter the pinkish coloration, brass has always sized and shot fine, in bolt and AR's.

 

[AlNyhus]

Interestingly, I have found that if a case is primed with a live or spent primer, and not loaded with powder or a bullet, when fired, the force of the firing pin will bump the shoulder. If it is fired again, the shoulder will bump more. I was able to bump the shoulders back an additional 0.005” - 0.006” on some cases.

Yep. Each time you do this, it makes a bit more clearance and that makes it easier the next time...the case gets a 'run' at the shoulder area of the chamber. -Al