To all,

I am about to venture into my first case forming project - I want to make some 300 H&H mag cases. My limited understanding is that this is possible and best accomplished from 375 H&H cases. Will carefully running well lubed 375's into a 300 H&H die (RCBS) work to do this. Am I missing or not understanding anything? Should I use a different parent?Please let me know.

Thanks, Vlad

Vlad,
well, you COULD do that... what country are you in? midway has outposts in most places and will sell you 300 hh brass

jeffe

It's a lot of resizing to go from .375 diameter brass to .308 diameter brass in one sizing.....it'd be good to go to .35 cal then to .338 cal then to .308 cal.....It might work.....I doubt it. I suspect you'll have a lot of rejects.

Strongly advise getting new brass.

Thanks for the replies. I'm in the USA so, I know I can buy 300 H&H brass new. I just have a bunch of 375 H&H brass sitting around so, I thought I'd make a first attempt. Sounds like maybe I'd better just buy some ready made brass and try my hand at reforming on some other caliber. Thanks for the info.

-Vlad

The issue you'll face with the .375 to .300 conversion is not so much in reducing the neck, which is likely no problem, but in squeezing the slightly wider (and heavier) shoulder down to the more tapered shape of the .300. Still, this shouldn't take that much "elbow" if your dies are smooth and you use the proper lubrication, AND your .375 cases are not work-hardened from multiple firings. If so, they may need a judicious annealing of the neck-shoulder area, but this is a touchy undertaking and you need some instruction on how it is properly accomplished.

TIP: Don't "bottom out" your .300 FL die. First, start with it about .02" off of the shellholder and see if the resized case will enter your rifle's chamber. If not, screw it down in increments until the case chambers with just a tad of resistance as you turn the bolt down. This will assure that you have minimal headspace and will provide the longest case life and most satisfactory performance.

Stonecreek,

Thanks for the vote of confidence and the tip about acquiring proper head space. I will give it a try. All I have to lose is some brass that is just sitting around anyway. I will let you know how it goes.

-Vlad

Well, I gave it a try. Not a great success. As someone mentioned, getting the correct neck dia. was no problem - it's that shoulder that causes the problem. I tried following the tip by stonecreek - still couldn't get any ability to chamber in my rifle. Guess I'll just wait and hope Winchester offers some 300 next year. Thanks to everyone for their help.

-Vlad