While talking to Remington I found out that 375 RUM brass will not be available until about a year from now.

Thus, to satisfy my reloading urges, I thought of perhaps fireforming some from 300 brass if possible.

Will this simply be too much of a stretch resulting in split cases?

Any opinions are appreciated. Also suggestions on doing the forming are welcomed.

Herb D,

That is easy to do. I would probably expand to 338 first but not necessarily. The sharper the shoulder the less necking up (or down) you can do in one go. Very sharp shoulders collapse under the load. I would think the 30 degree shoulder of the RUM cases is right on the borderline.

I have found the RCBS expander plugs very good, the Hornady eliptical plugs not so good.

The main problem with necking up (as opposed to necking down, but here you have no choice) is that the neck is thicker just above the shoulder.

This occurs because part of the shoulder of the 300 RUM cases become the lower part of the neck for the 375 RUMS.

However, this should be OK, unless you havea chamber with small clearance between the case neck and chamber wall. I would not expect this to be the case with the 375 RUM.

You may however, see a slight bulge at the lower part of the neck.

Cases will also shorten but that is OK.

Also, saw your post on the rechambering to 7mm and 375 Ultra. I guess the rifles were 7mm Rem and the 375 H&H. You should expect no problems at all.

In a nutshell, your only concerns are your ears with the 7mm and your neck with the 375

By the way, if the No 1 was in 375 H&H, how did it shoot as I am about to buy one.

Mike

Hi Mike,

Thanks for the reply and the appropriate warning!

You're right on the calibers. I never did shoot the 7mm Rem. so I don't know how good the barrel is.

The .375 had a couple hundred rounds through it. Accuracy wasn't that great mostly through my misdoings and partially due to a cheap scope that the rifle came with. I started out with 2 1/2" groups and on the last outing with it I got that down to 1" & 1 1/4" with one problem. The cases stuck in the chamber and had to be persuaded with a ramrod. Primers looked OK. The load at the time was a medium one but with surplus IMR 4895 powder that I had never previously used.

One problem I noticed with the rifle was that it copper fouled very fast. Someday I'd like to fix that by rebarrelling it with a highgrade match barrel.

Otherwise the #1 in .375 is a nice rifle and one that you would enjoy. I guess I'd better say that since it got me my "first elk" last year with a 425 yard shot.

I have always necked down before and never up so this will be a new experience for me and will cause me to crack a few books to learn the procedure.

Herb

What's the case length on the 375 RUM? Will the 300 cases be a little short after expansion?

Don

Don G,
Good question, Don. 375 RUM cases are supposed to be the same length as the 300 RUM. Perhaps someone who has done this or something similar can give an answer.

Also, how much of what powder shoud I use for expansion? I also understand a filler is used over the powder. What does that consist of? I suppose a wad is used to separate the powder from the filler? None of my books mention this procedure.

Herb

P.S. I'll be away from the computer for a couple of weeks. In the meantime, I'd like to thank all who contribute to this topic. Hopefully, I'll have the rifle by then to get started on reloading.

I just put a caliper on a few 375 Ultra cases just to be sure. They averaged 2.840" and I think the 300 Ultra is the same while the 338 Ultra is the oddball at 2.750".

Hope that helps, Joe.

Joe,
Thanks for the help, I was wondering if it would be full length.

If you could see your way clear to making me 5 375 Ultra dummy rounds for action work, I sure would appreciate it. If I could choose, I'd ask for 3.65 COL with round nose 300 grain bullets, spent primers and 100 grains of filler. But I'd take just about anything.

Just hit the email icon at the top of this post if you're willing.

Thanks again,
Don