can you make 7 STW cases by running 8mm mag cases in your 7stw dies or running 375 h&h cases thru 7stw dies if so do you have to do anything else to them thanks in advance

Being the brass whore that I am, I picked up some winchester 375 H&H at the range the other day.. Was wondering how difficult it was going to be to neck these down? Hope you get an answer?

The shoulder won't be full diameter until you fire the cases once in your chamber. Whether you do this with small loads of bullseye powder topped with cream of wheat or starting loads of your normal powder in a normal firing is up to you, but the tapered 375 H&H case needs to be blown out to form a full diameter shoulder for a 7mm STW case.

I've been necking down 7mm Rem Mag cases in my .257 Wby Mag die and it is working great. I hope you have as much luck in your venture. The 7mm Rem Mag cases are a lot cheaper than the Wby cases.

The 8mm to 7STW should be no problem, the 375H7H all the way down may not work unless done in steps (like down to 30 then down to 7mm). All would have to be fireformed & trimmed (the case will elongate some). I've sized 35whelen to 338-06, works fine.

Tens, if not hundreds, of thousands of rounds of 7mm STW were made from 8mm Rem brass prior to the STW being adopted as a factory round. It is so simple that if you accidentally picked up a properly lubricated 8mm Rem case and ran it through your 7mm STW die, you probably would never realize it until you looked at the headstamp.

I have also made 7mm STW from .300 H&H. The case looks a bit odd until it is fired, after which it is indistinguishable from a factory-born 7mm STW. .375 H&H would work similarly, except that the greater reduction in neck size might (or might not) require thinning the necks.

A word of caution: Both of the H&H cases seem to be in tight supply right now. You might very well sell or trade any H&H cases you have for 7mm STW and come out ahead.