Bolt Face pitting
- Thread starter GMC403
- Start date
I have several bolt heads with this unfortunate experience. Tone down the loads, and those bolt heads and brass will last longer. Confirmed by my science anyway that as brass gets older (espectially with FC brass) and primer pockets get loose then expect pitting to come your way. Hot loads and loose primer pockets then you should expect it will happen. Also, excessive headspace and primers backing out during expansion may cause this too (fire forming looser than expected chambers). Excessive pitting and hotter loads will push brass/primer cup into the imperfection. Stick with the better brass (Win, Norma, Lapua, LC).
No biggie with those pits you have. If they are rough to the the touch then a little JB and a soft dremel tool will polish out some of the imperfection by my experience. My 2c
No biggie with those pits you have. If they are rough to the the touch then a little JB and a soft dremel tool will polish out some of the imperfection by my experience. My 2c
bearkilr
CGN Ultra frequent flyer
- Location
- Nowhere, ......just past the middle
Winchester brass maybe. Loose pockets, I had an issue with 270 WSM, new brass. Lots of reports on the net about it. Fed 215 primers which were fine in all other brass I used them in. Good picture!
To agree with everyone else, and add some photo proof of what is happening... yes, you are getting primer failures, and the gasses are cutting into your bolthead. If you kept your brass you would almost certainly see that the primers have a pinhole failure in them, and there is heavy fouling around the primer ring.
This happened to me on some modest .338LM reloads using Winchester primers, I had fired many hundreds of them before without issue, but with a new box of primers I got 3 primer failures in the first 100 primer box. I scrapped the box of primers and changed brands, no longer use winchester primers on my magnum rifles.
Rifle bolt is slightly scored, but has not effected function at all for many hundreds of rounds.
This happened to me on some modest .338LM reloads using Winchester primers, I had fired many hundreds of them before without issue, but with a new box of primers I got 3 primer failures in the first 100 primer box. I scrapped the box of primers and changed brands, no longer use winchester primers on my magnum rifles.
Rifle bolt is slightly scored, but has not effected function at all for many hundreds of rounds.
To agree with everyone else, and add some photo proof of what is happening... yes, you are getting primer failures, and the gasses are cutting into your bolthead. If you kept your brass you would almost certainly see that the primers have a pinhole failure in them, and there is heavy fouling around the primer ring.
This happened to me on some modest .338LM reloads using Winchester primers, I had fired many hundreds of them before without issue, but with a new box of primers I got 3 primer failures in the first 100 primer box. I scrapped the box of primers and changed brands, no longer use winchester primers on my magnum rifles.
Rifle bolt is slightly scored, but has not effected function at all for many hundreds of rounds.
I have to question those "modest" loads in the 338 LM. Good lord man can you not see the craters around the firing pin mark on the primer??? That is a classic indicator of high pressure. Along with the hole cut through the edge of the primer. Several high pressure loadings have expanded the primer pockets allowing high pressure gas to cut through. Look at the brass transferring on to the face of the bolt. Another indicator of excessive pressure. Keep that up and you are headed for a wreck my friend.
They were non magnum primers I was using at the time, and those winchester primers would flow like that around the firing pin at anything above minimum load specs. Other brands of primers did not flow like that, thus why I have swapped brands. I assure you these loads were reasonably modest. As for the brass transfer, yes, those were from a small batch of test loads that ended up being too hot, scrapped em, pulled the bullets and started over. Same goes for the plunger marks, those brass are just about ready for the cull. Still, it is the primer that failed in that case, not the brass.
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Ya, fairly common. I've noticed lots of surplus Mausers with similar marks.
You'd think military ammo with sealed and crimped primers wouldn't leak though, but they do.
Is the rifle in a caliber that could have seen corrosive ammo?
Could it be maybe a bit of excessive headspace? If the cartridge is pushed forward even slightly the primer can back out and leak, but it gets re-seated after the case expands? Is there any flow of the primer into the firing pin hole?
Just an idea....
And those .338's.. yikes! You can see the ejector plunger mark too.
You'd think military ammo with sealed and crimped primers wouldn't leak though, but they do.
Is the rifle in a caliber that could have seen corrosive ammo?
Could it be maybe a bit of excessive headspace? If the cartridge is pushed forward even slightly the primer can back out and leak, but it gets re-seated after the case expands? Is there any flow of the primer into the firing pin hole?
Just an idea....
And those .338's.. yikes! You can see the ejector plunger mark too.
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