I have a lot of Norma basic mag brass. I haven't checked dimension, but can I form the375 from that Brass or should I just buy new? I have case forming dies and could do it if the basic brass is basically the same.

Case forming dies are a waste of $ for this. But 375 brass is easier to get than basic brass so I would sell that and just buy some. Less work.

I believe you can just run a case thru the 375 die, or perhaps better a 416 REm and then a 375, so custom case forming dies are not necessary,If I recall..but if you have case forming dies, Im sure your good to go...

I used to make 375 and 416 Chatfield Taylor by hacksawing to a tad over length then running them through the 375 CT and 416CT dies, trim and chamfer to specs, may have outside or inside neck ream, best I recall its been more than 60 years since I had the great Chatfield Taylors, a great caliber btw..

I would just buy new. Sell the basic brass to somebody who needs it. Case forming takes time and invites error, for no real benefit in your case.

Rem and Norma 375 H&H are out there.

I will look for brass. Not interested in selling the brass. Some may remember that I made and sold a case forming die set. Case forming is not difficult with the proper knowledge and tools.

I think there is some brass on gunbroker

Sometimes you have a brain fart. One of my good buds owns a little gunshop. said he had brass and bullets. He owes me a little. Thanks for your ideas. I cut the barrel at 22". It is on a CZ550.
Just need a good stock now.

Save that basic brass for your 450 Ackley build.

Yea, you will want one in the future.

I have tons of 375 brass for my three 375 rifles. It is easy to find. Noticed some on the Campfire a few days ago.