Primer blowby

[Zombie1978]

I was shooting my 30/30 the other day with cast loads. I had one case have primer blowby. Do I need to discard this case or try to reload it again? What could cause this and what can I do to remedy it? It has only happen with this case and no more. I don't tumble my cases I wash them and clean primer pockets with the lee tool.

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[Scharfschuetze]

My guess is the primer pocket has expanded beyond normal specs and the case just needs to be thrown away. That's just a normal occurrence and nothing to get too excited about.

You don't want any gas getting by the primer as it can pit your bolt face.

[Echo]

Plus One...

[Zombie1978]

It pitted the face of the bolt a little. The load I was running was 18gr of H4198 and a 150gr cast bullet. The case had only been fired once the primer was tight going in. The first one I have had do this.

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[Zombie1978]

Here's a picture of the primer and case. The primer pocket is still tight but the primer has a small crack in it.

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[MT Gianni]

Clean and seat a new primer. If it doesn't seat with minimal force, just slips right in toss the case due to an oversized primer pocket.

[tradbear55]

Maybe a faulty primer is the cause. Primer cup may have been to thin to withstand the pressure. I would reload and try that brass again. I would keep it separate from the rest. If it happens again toss the case. They're not really that expensive in the bigger picture. Far cheaper than replacing the bolt on your rifle.

[Zombie1978]

It was a Winchester primer. It had a very small crack right a the corner. I think I will try CCI primers next.

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[Scharfschuetze]

I had similar experiences in both the 7.62 NATO and a 357 Magnum rifle. Divits in the bolt face from both of the cracked primers.

[quack1]

Winchester had some problems with primer cups in large rifle primers. Leaks at the radius of the cup, just like the OP's picture. Call or email customer service.

[Digital Dan]

Some of the Winchester SRP are doing the same thing. Sadly, I have a couple thou of each. They are relegated to menial tasks...mouse fahts and such. Dang it.

Rest of the world is CCI and Federal..........

[Tatume]

Winchester had some problems with primer cups in large rifle primers. Leaks at the radius of the cup, just like the OP's picture. Call or email customer service.

+1 Winchester replaced a case of 5000 for me because of this.

[mdi]

You've gotten most of the possible causes, what to look for, but I'd just toss it. It's just one case in a very common caliber. Toss it.

[Tatume]

The case is not the issue. Every time one of those primers leaks it etches the bolt face. If you only have a few hundred primers in the batch, toss them. If you have several bricks, call Winchester about replacement.

[fredj338]

I had similar experiences in both the 7.62 NATO and a 357 Magnum rifle. Divits in the bolt face from both of the cracked primers.

That was likely a primer too hard for the load, primer doesn't expand to fill the pocket. Something else to check is headspace issues. This can allow a primer to walk out a bit. In a primer pocket that has been overly reamed, could also cause the leak. Also make sure it was not a pistol primer.

[hydraulic]

Went down and pulled the bolt on my O3A3 and sure enough, there is pitting on the bolt face. I had heard of this possibility before, but didn't put much credence in it. Couldn't believe a primer leakage could affect the steel bolt. I shoot about 40 rds. a week from this rifle, SR 1 target, and have never been particular about my brass; some commercial and some military, and all of it has been around a long time. In fact I normally will lose two or three cases to neck cracks each reload. I have been accustomed to primer leakage as a common occurrence and just recently quit reloading military cases because when reaming the primer pockets it is almost impossible to get them the same, making the pocket oval shaped instead of round. I have a couple hundred Lake City 67 Match once fired empties back in my stash, so I'm going to send the other four or five hundred to the scrap yard. I'm 79 and have been collecting this stuff for forty years. I used to buy surplus 'O6 at the gun shows, Saint Louis 43, Denver 42, Eau Clare 43, etc. for 2 or 3 bucks a box, and I have been reloading them ever since. As for the bolt, I can't imagine that the pitting can be a safety hazard.

[Scharfschuetze]

That was likely a primer too hard for the load, primer doesn't expand to fill the pocket. Something else to check is headspace issues. This can allow a primer to walk out a bit. In a primer pocket that has been overly reamed, could also cause the leak. Also make sure it was not a pistol primer.

No Fred, that isn't the case as those were full power loads for match shooting with the 7.62 NATO and hunting loads with the 357. Headspace on both rifles was/is spot on as proven by head space gauges as well as thousands of rounds fired between the two rifles.

The issue was poorly made primer cups. Either too hard or too thin. Hard to say which at this point as the cases and cracked primers are long gone. While primers are of superlative quality on average, it's always a possibility with every shot for one to let go. I see the evidence every now and then when looking at used rifles, particularly match rifles that get a lot of rounds through them. I always check the bolt face and now and then... there's a divit.

When the 7.62 NATO round's primer let go at the 600 yard line, I knew immediately something wasn't right. I could actually smell what I assume was burnt steel from the bolt face.

[Tatume]

Actually, I think the issue is caused by chemically cleaning the primer cup during manufacture and failing to completely remove the solution from the brass. The inside of the cup is slightly etched, resulting in a weakness that perforates on firing.

[44man]

Federal had a problem batch and it was traced to the cleaner. It corroded the cup. Tatume is 100% correct.

[leadhead]

I had the same problem with Federal primers years ago, and they totally ruined
the bolt face on my XP-100 in .308x1.5 Federal told me they must have been
stored in a acid vapor room. They never admitted it was there fault. I never
used Federal primers again.
Denny