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Dear Sir, Would someone explain what exactly does primer erosion do to the face of the bolt. What it looks like. Is the bolt still usable? I have a TRW bolt that has (what I have been told) primer erosion. Looks like tiny punch marks in a circular pattern where the primer leaves a brass colored mark. Thank you, czjet
 

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Dear Sir, Would someone explain what exactly does primer erosion do to the face of the bolt. What it looks like. Is the bolt still usable? I have a TRW bolt that has (what I have been told) primer erosion. Looks like tiny punch marks in a circular pattern where the primer leaves a brass colored mark. Thank you, czjet
Pics would help but it is probably nothing.
 

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Although this is not primer erosion, this is what happens when you blow a primer.



If it happens once, find the problem and don't continue to use the ammo. If it happens enough, it stops supporting the rim of the primer. I looked on my fired cases and the primer starts to flow into the craters once it's fired. I purged the batch of primers I had and I don't have the problem any more.

I don't know what the criteria is for replacing the bolt, but once you've had enough, I'd replace it. I contacted the primer maker and they paid for the damaged bolt.

Tony.
 

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I have had primer blow by on some once fired brass that had the pockets slightly over processed and had a bolt face that was pitted pretty badly so I just shot it until it got really bad then replaced the bolt body, small pits are usually not an issue.
 

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An even, etched ring the size of the primer is common.

Small pin punches, on the other hand, indicate flame cutting. There are numerous causes. Leaving ammo in the hot sun can cause overpressure, while storing primers or ammo near ammonia fumes will soften the primer metal. Manufacturing defects, loose primer pockets, the list goes on.

Either one of the above is 99% of the time a cosmetic issue. It would need to have some serious craters for it to be a structural concern. Pictures would help.

I would check the ammunition you are using.
 

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Discussion Starter #8
Sir, This is exactly what I have on a TRW bolt. Not as bad ...with less of the marks. Thank you Tonyben for the picture. Thank all of you for the help. czjet John T.
 

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Sir, This is exactly what I have on a TRW bolt. Not as bad ...with less of the marks. Thank you Tonyben for the picture. Thank all of you for the help. czjet John T.
Here's what causes the craters....




As you can see, it's not leakage around the primer pocket. It's the primer failing and blowing a hole which causes the scorches. Gas leakage around the seal creates the uniform ring, not the crater.

Here's a better view of the bolt.


If you're using Winchester WLR primers from a few years ago, switch them out. All that damage happened within a year. It was getting very depressing. I switched to CCI and Remington primers and haven't had a problem.

I ran across a batch and I had 3 blown primers in a batch of ammo I loaded so I reduced the powder charge. It kept happening with subsequent lots. I had used that recipe for years and all of a sudden, trip after trip, I was getting blown primers, no matter what powder charge I was using. Once I switched primers, the problem went away.

Tony.
 

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Tony, is there specific lot numbers that have the bad primers in them?
Or are these several years old and the lot numbers are long gone? I just found this thread today as I was researching reloading practices and I am quite concerned.

I have 2 boxes of these primers but they are recent purchases in 2014. I inspected them closely and saw no signs of corrosion or anything nasty.
 

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Tony, is there specific lot numbers that have the bad primers in them?
Or are these several years old and the lot numbers are long gone? I just found this thread today as I was researching reloading practices and I am quite concerned.

I have 2 boxes of these primers but they are recent purchases in 2014. I inspected them closely and saw no signs of corrosion or anything nasty.
I shot a bunch of winchester primers I purchased them right after sandy hook never have any problems with them. But I will never buy any more Winchester primers. I am sticking with Federal only.
 

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I've quit using Winchester primers also. They just don't "flow" through the Dillon primer tube nearly as well as CCI primers do. Keep jamming up.
 

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Tony, is there specific lot numbers that have the bad primers in them?
Or are these several years old and the lot numbers are long gone? I just found this thread today as I was researching reloading practices and I am quite concerned.

I have 2 boxes of these primers but they are recent purchases in 2014. I inspected them closely and saw no signs of corrosion or anything nasty.
I don't remember the lot numbers. I loaded a whole bunch and threw the boxes away. It wasn't until the next year that I shot them. The primers would have been bought somewhere between 2009 through 2011.

Tony.
 

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I have had the whole primer pop out on an AR15. They are Winchester military overrun 55 grain in the white 20 round boxes that I bought in the mid nineties. I think they went on the market because the military switched to the 62 grain round.
It happened three times in a hundred rounds fired. I thought it might be the bolt ?
Then it happened to another AR15 I own.
If that would have happened to a soldier in combat he would have been screwed.
I had found that some of the popped out primers fell inside the trigger/hammer area.
One time one lodged under the hammer jamming it. I had to remove the hammer to get it out !
This has now happened 5 or 6 times in about 300 rounds. It hasn't etched into the bolt faces yet.
The lot number is stamped on the boxes. I have only 1700 rounds to go !
 

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The only other thing I don't think was mentioned doesn't derive from primers per se, but you'll run into bolts that were once welded up for a drill rifle and later the weld was ground off and the bolt may or may not be safe or in spec now. Discoloration around the firing pin hole is the usual clue.

Those M14 bolts that look like a squirrel has been nibbling around the hole, that's primer erosion/corrosion or gas blowback. The mystery is why, b/c very, very little corrosive primer 7.62 NATO or .308 Win ammo was ever loaded up militarily or commercially so far as what's known to us.
 

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79 IHC Scout II, 74 VW Bug class 11 look a like
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CCI had a bad batch of .50 BMG primers back about 5 years ago, screwed up a bunch of very expensive target rifle bolts. I saw one bolt that looked like you used a plasma cutter on the bolt face, these were primers in a blue and white box.

Casey
 

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Federal had a bunch of 210M's, about 20 years ago,that did the same thing. They replaced the unused product and repaired some pitted bolts also.
 

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To expound a little on tonyb's first post, once you form a decent cavity behind the primer, you're going to see more and more blown primers because they aren't supported. Similar to when the firing pin pierces enough primers. If you see it once, pay attention and fix the issue.

You can also leak gas around the primers with hot loads. As pressure increases, the primers flatten (which may be normal depending on the primer) and start to flow outward to fill the fillet of the primer cup and back into the firing pin recess (cratered primers pretty much always mean too much pressure). After that, they start leaking gas around the edges.
 

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79 IHC Scout II, 74 VW Bug class 11 look a like
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I have also seen blown primers from using a case deburing tool to cut out the crimp, I only use a swaging type tool to remove the crimp but I do give the case a light turn of the deburing tool to remove any sharp edges in the primer pocket.

Casey
 
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