Didn't want to hijack Duane's post but an curious as to the reasons for gas cutting.

Usually, excessively high pressure handloads. Blown primers, etc., etc., etc. Same folks who hop up car engines beyond design specs, then blow them up and wonder, WTF?

Yes, it's always idiots who exceed the limits of their brass and primers. Regardless of what the book says. Caused by gas finding it's way past the primer.

There were a bunch of Winchester primers with bad cup which would pierce and cut divots in the bolt face. The leak occurs at the edge of the primer pocket. This happened with normal loads. In combination with the setback though, I doubt the issue was anything but hot loads in this case. I just mentioned the primer issue because I've seen it. I have a divot in the face of my own 1935 Mauser and it wasn't loaded too hot! I have relegated those primers to black powder loads. Regards, Bill.

What Bill said.....

I've two bolts, on two rifles, whose faces were flame cut by ONE shot each......on a PD trip years ago, via a tiny hole in the corner of the fired primer.
The only common factor.....one particular lot of Fed 205M primers.(Note: the problem is NOT limited to any particular maker.)

The problem has been long known in benchrest circles. Seems that, over the years, the primer cup metallurgy among different manufactureres has "varied".

I ended up unloading and reloading about 400 rounds, across 3 rifles. Still have those "bad" primers somewhere.

BTW.....Bill, I wouldn't trust those primers....even in a BP application.

Hope this helps.

Kevin

These primers....



caused the gas damage on the face of this bolt...



Not high pressure loads. Happened while working up loads.

The gas cutting I', familiar with soft cast bullets or hard cast bullets that are sized to small. The gases just cut around the bullet, vaporizing the the lead creating a channel for the gas.

Primers that have been contaminated by contact with ammonia fumes will do this as well with standard pressures. Happened to me years ago with some Federals I had sitting on my bench in the man cave. I used the room for ammonia fuming of some maple and 6 months later I noticed my M14 bolt face was gas cut all to hell by primer leakage after just one string of fire. Sent a letter to Federal (this was way before the internet!) and they requested I send the primers in question to them for testing, etc. They called me on the phone a few weeks later and were specifically interested if they had been exposed to ammonia. Primer cups are brass and ammonia attacks brass making it brittle. They called it "stress/corrosion cracking". They have seen this caused by many forms of contact. Full blown exposure as in my case with 28% stronger ammonia, and even reloading rooms in close proximity to diaper pails and cat boxes. Most bore cleaners can attack brass and copper, etc.
Since then (1990 or there about) I keep all primers and percussion caps in GI ammo cans with good gaskets. Never had a problem since, even with some stupid hot loads that loosened the pockets.

Some time it is just primer quality control. I have picture some where of one that made it through. The blank the primer was punched out of was not round. It left a open line on the side of the primer that let gas leak back and cut the bolt face. The loads were not hot, none before or after.

As I said, it is not always high pressure; it is the combination of primer or brass that are not sealing. And it is not always too small primers; they do obturate and seal. Or are supposed to.

Found the pictures. Forgive the quality! Best a pocket camera can do. Back when the Blackberry was king! Dark line from the hole to the edge of the primer cup was an open seam.


You can see how the super heated gas worm holed the case. Cut a small divot in the bolt face.

I received an AR 10 in the shop with a bolt that wouldn't go to battery. I remove the bolt and disassembled it to find it clogged with 25 + pieces of brass that used to be primer cup indents.

quote:

Originally posted by dpcd:
As I said, it is not always high pressure; it is the combination of primer or brass that are not sealing. And it is not always too small primers; they do obturate and seal. Or are supposed to.

What do you think? Haven't reloaded in years, but seems to be there was a slight but definite resistance to seat the primer.

Average reloader would notice a lack of resistance if the pocket was expanded or undersize primer??

I was using a Lee hand priming tool. Put the primers in, shake to align, install cover and prime. There is a little bit of difference in the "feel" on primer pockets but not a "whoa" what was that. I now use the arm on my single stage press and look at each primer. Still using the same 1K lot and have not found another!

Yes a normal primer to pocket fit will have a resistance to it. Halfway knowledgeable reloaders should notice a loose pocket. And yes, much more noticeable with a hand tool.

An example of what we're up against: Years ago, I worked for a big firm in Hayward CA..Some stumbler bought a coup[le 1100's...12 and 20 ga...AND a bunch or reloading equipment,

Sure enough, he put a 20 ga round in the 12 ga chamber didn't go "bang, so stuffed a 12 ga load behind it with predictable results

Sued (why not) and jury actually awarded him 10K!!


If you looked this guy in the eye, you could see the back of his head..NO BRAINS!

When the jury was polled..."We felt sorry for him"