Inconsistent Case Rim Diameter

[Dfin385]

Hello experts,

I bought some mixed head stamp, once-fired 7.62x39 cases and quite a bit of it was Belom, which I’ve never used before. After full-length resizing, I found that about 20-25% of the cases didn’t fit perfectly with the case head in a Lyman case gauge. Specifically the head sat proud of the gauge. On closer inspection, it seemed that the “hang up” was that the diameter of the case rim was larger on those cases (.448-.449). I tested the theory by sacrificing a few cases and filing the outer edge of the rim. They fit perfectly in the case gauge after filing. My first thought was to discard the ”bad” cases. It has me curious enough that I thought I would ask here to see if there are any other thoughts. For example, would you expect the “fat” ones to chamber safely or is it just not worth it to try?

Thanks!

 

[jackieschmidt]

If removing a small amount from the rim OD brings them to standard, I see no reason why it would hurt anything.

Are you filing them by hand, or spinning them in some manner to file down the size. Keeping them even all the way around would be the only concern.

 

[AlNyhus]

As Jackie said, as long as the diameter stays even you're fine.

I had some Norma 220 Swift cases that were too big to fit in the shell holder...they measured .475 across the rim. I wrapped tape around them, lightly chucked them into a drill clamped in my bench vise and with the drill locked on, hit the rims with a strip of 160 grit crocus cloth. Worked fine.

 

[divingin]

After full-length resizing, I found that about 20-25% of the cases didn’t fit perfectly with the case head in a Lyman case gauge.

Try them in your rifle. If they fit your chamber (or given that the problem is the rim, your bolt), there wasn't a problem to begin with (other than using the case gauge, that is...)

 

[Doom]

I have encountered this issue on a couple of occasions and it can be the result of high pressure loads that stretch the the unsupported portions of the base. It is not an issue as long as the rim can still fit into the extractor. I shot a number of LC 308 cases last week that had this issue. They cycled fine.

 

[butchlambert]

Reminds me of a match in Arkansas several years ago. I had the same problem. I couldn't get them in the shell holder. After fighting it for most of the morning, Jay Lynn Gore handed me another shell holder. For whatever reason I had the wrong one in my press.

 

[barefooter56]

Hello experts,

I bought some mixed head stamp, once-fired 7.62x39 cases and quite a bit of it was Belom, which I’ve never used before. After full-length resizing, I found that about 20-25% of the cases didn’t fit perfectly with the case head in a Lyman case gauge. Specifically the head sat proud of the gauge. On closer inspection, it seemed that the “hang up” was that the diameter of the case rim was larger on those cases (.448-.449). I tested the theory by sacrificing a few cases and filing the outer edge of the rim. They fit perfectly in the case gauge after filing. My first thought was to discard the ”bad” cases. It has me curious enough that I thought I would ask here to see if there are any other thoughts. For example, would you expect the “fat” ones to chamber safely or is it just not worth it to try?

Thanks!

European made cartridge cases are made to CIP specifications that are "close" to SAMMI specifications but can cause issues like this with case gauge and shell holder fit. So if you experience these issues the brass is not " defective". Just different and in the case of the shell holder the only fix is to modify or find a shell holder that works with your brass. REDDING RELOADING can help with this with their shell holders. We worked with them back in our SINCLAIR INTERNATIONAL days in regard to the shell holder issue and they modified the manufacturing process to help with the thicker rims.

 

[ebb]

Early RCBs and others made shell holders for 338 Lap that would not let Lapua brass fit. they made another that was a different number that worked perfect. Stacking tolerances would be my guess. Keep filing boxer primed 7.62 -39 brass is hard to find and pricey when you do.