IMI .357 mag brass question


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gamestalker
April 20, 2013, 08:30 PM
I recently come into some new IMI .357 mag brass and am pretty puzzled right about now. Every 3rd or 4th case into the expander / belling die, the case will seize up in the die. I can fell as each round leading up to this event increases with resistance. So i took the expander apart and the plug had a lot of brass piled up on it. I cleaned it with some fine compound, took about 4 or 5 minutes to get it off, it came off very easily. Once again the brass was seizing up. Problem is getting worse when priming. The IMI brass will not accept a primer at all. The primers are getting mangled? JSmith had some similar problems with PMC brass?

So I decided to see what would happen with another case head, not IMI brass. I ran a large amount of mixed brass through resizing, belling, and priming, everything went off without a hitch and was normal.

Anyone have experience with IMI .357 mag brass. I've been loading the .357 for decades and have never had anything like this happen with brass, I'm stumped. This brass is definitely not in good spec. and at the very least I will need to do some primer pocket work to get them fired for the first time.
GS

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ReloaderFred
April 20, 2013, 08:40 PM
I had the exact same thing happen with brand new Starline .38 Special brass, and ended up pulling a couple cases in half when I lowered the ram, and ruined a bunch of the others due to excessive stretching.

The problem is the brass is bare, like in cleaned of all lubricants. Bare brass sticks to steel, rather than sliding on it. If you lube the brass, the problem will go away. I just tumbled the rest of the thousand rounds I had in corn cob, and that imparted enough "lube" to make them work. Fired brass has residue on the inside that acts as a lubricant.

As for the priming issue, I've never had a problem priming IMI brass in any caliber. You might run them through the primer pocket swager if they don't have a slight bevel on the mouth of the pocket.

Hope this helps.

Fred

gamestalker
April 21, 2013, 01:56 AM
That's exactly what my first suspicion was that it was dry bare brass. That's how they felt when I ran it into and out of the expander die too, not to mention the screeching sound they made when coming out of the die. I solved the problem though, since I'm loading jacketed bullets, I'll just seat them without belling. I actually load all rimless cartridges without belling, and have actively used the same method for rimmed cases over the years. So no biggie I guess.

I did figure out the priming issue though. It turned out to be a small piece of debris on the priming tip that was collapsing the center of the primers. I had glanced at the tip when doing my initial assessment, but the debris was quite small, and my eyes are quite bad, go figure.

GS

ReloaderFred
April 21, 2013, 02:25 AM
Glad you got it worked out. Several people have had that problem with new brass, but usually when you mention the brand, people jump up and down and say it has to be something else, as that brand of brass could never have a problem. It's mechanics, plain and simple.

Fred

Steve C
April 21, 2013, 05:24 AM
New cases and newly trimmed cases have a very square cut mouth with sharp edge and when worked you will break off small wire like pieces from this edge. This will cause the expander to stick and spread the wire debris around. Simply run a chamfer tool inside and outside the rim before working the brass and the problem with these small pieces of brass will go away. You don't need to work the chamfer hard, just a quick turn is enough to break the sharp edges off the case mouth.

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