Okay, finally scored 20 cases in 375 Ruger.

I want to neck down to 30 cal. with a .338 neck OD, a neck length of .280, a case head to shoulder length of 2.20 which leaves a shoulder to neck base of 0.10. All from the original length 2.58.

I load my 280AI and 35 Whelen but have never changed cartridge dimensions before other than fireforming.

Any advice? Other than why another 30 cal. cart.

Ted

It should be a simple neck down and fire form. You may have to take the neck down in two steps. Say, first to 338 and then to 30? Your base to shoulder dimension will be greater than the parent case so you will need to neck down only until you have a crush fit and then a stiff fire-form load should do it. The neck thickness MAY grow a little so you need to be aware of that. Finished neck diameter MAY be a little more than your target of .338.

Good Luck

Ray

If you want a OD of .338" just subtract bullet dia of .308" that leave neck thickness at .015" so you need to measure neck thickness on cases you have to see how that matches. I alway get neck dia of the chamber first then work the numbers down. I agree with Ray on necking down in steps plus his other comments and it's a good thing after the first firing to inside neck ream to elimate that thing call the "dreaded donut".