When necking up 7mm or .300 brass to .338 I have noticed the same thing with the slightly rounded (not sharp) shoulder. After the first firing it is noticeably sharper. However, I have not found any difference in accuracy or velocity in the "fire forming" rounds.
375 RUM brass
- Thread starter turkn8r1
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When necking up 7mm or .300 brass to .338 I have noticed the same thing with the slightly rounded (not sharp) shoulder. After the first firing it is noticeably sharper. However, I have not found any difference in accuracy or velocity in the "fire forming" rounds.
Rifleman513
Well-Known Member
Okay well that clears up that question. Now I just can't figure out why the nickel plated federal brass works just fine but both new and once fired nosler brass wont chamber...
I don't know. Maybe the brass cases are experiencing a little spring back and the nickel plated cases don't.
I had the same thing happen to me. I was necking up .300 RUM brass to .338 and pushing the shoulder back to make .338 RUM. I have two sets of .338 RUM dies and neither would push the shoulder back enough to get an easy bolt close, it was pretty stout to close if at all. I made a brass shim from an old piece of brass (that was .016" I believe) and put it under a piece of brass in my shell holder. After running it through my FL sizing die the brass chambers perfectly, and I've only had to do it that initial time.
Rifleman513
Well-Known Member
I may try that and see what I can figure out. Thanks for the help.
I've had decent luck necking up 7mm RUM as far as 375 as long as I go in steps to 30, 338 then 375 and anneal at least twice in the process. It's easier to just form brass from 404 Jeffery cases. The Jeffery brass comes out with a slightly longer neck too.
GelatinousPig
Active Member
I keep reading about folks using 404J, but I have to ask about the slight differences in the case head. The RUM appears to have a different angle in the extractor groove, and the case width is slightly different. Do those matter when it come down to it with concerns of pressure and extraction?
Rich Coyle
Well-Known Member
Good question.
I've never had an extraction issue when running the Norma 404 brass in my 375 BME which is built on a Savage target action. Every round has fit the bolt face with no issue.
Overall the 404 brass holds up better than the Remington 375 RUM brass in my experience. In my 375 BME, I can run the same powder charge in both the 404 and 375 RUM base brass and get 3 firings from the RUM cases and 7 from the 404. These are not small powder charges either!
