Flat primers... sign of over pressure

[BasicMagic]

1. If it wasn't for the bent rim, people would advise bushing the bolt face and continue. Since it's a floating pin, it probably looks worse than it actually is.

2. As for the area circled, I am not convinced that's an extractor mark. Even if it is, extractor marks on once fired military brass are common, so unless it showed up on other brass, I would file it in the watch for it again department.

3. It can be difference of opinion on priorities or what the tea leaves say, but if you're trying to diagnose pressure issues with primers and brass like what's pictured, you will never be able to guess chamber pressure issues until you get rid of the over gassed issue. If the gas had been turned completely off on that shot, the case would look completely different, and different opinions would be formed.

4. Knowing the load would generate another set of opinions.

5. In a gas gun I can put together proof pressure loads that will exceed 75,000 psi in the chamber with muzzle pressure so low, below 4000 psi, the bolt wont budge.

40,000 psi loads that will hyper cycle so fast the magazine can't feed the next round.

With a little work probably put together a 55,000 psi load that will look like the photo.

6. All I am saying is in my opinion, unless that was a 5% over book load, I would get the gas system working correctly, before even trying to guess if it was over chamber pressure.

7. Of course this is all based on the assumption, that round was extracted by firing. not with a hammer and rod. But if it stuck that hard, I don't think the primer would have held.

1. After doing load dev for 9 different AR platforms both 15 and 10 I have never seen cratering that bad that wasn't at the high end of pressure. It might be a terribly sloppy firing pin hole but I doubt it.

2. The op of the photo states thats where one is located. You are correct though that I assumed it was that shot that produced the extractor mark. Though if that case was tumble cleaned those light ejector marks found on factory loads typically disappear.

3. Partly true. Might be first shot on a new gun and did not have chance to fiddle with settings. The presence of both cratering and ejector mark make me think otherwise though.

4+5. Yep.

6+7. You may be right as a boutique round like 375 raptor may lead someone to put a handload down the pipe as the first rounds on a new gun.

Overall though there is only one indication of bad timing. Bent rim. There are 3 possible indications of high pressure. Ejector mark, primer cratering, and bent rim.

The ejector mark can be caused by excess headspace, the cratering by sloppy pin hole, and the bent rim by bad timing due to rifle parts or settings. But all 3 can be caused by high pressure.

The fact that all 3 can be explained by one condition makes it more likely to be the correct one statistically speaking. But you are right its all speculation without the rifle and load known.

But if I had to put money on it, I'd bet pressure due to the alignment of symptoms.

 

[Bill K]

If you check and read any of the loading manuals on reloading, by numerous authors/companies, you will see the answer too your questions is "Yes", back off and play safe and sound.