I am trying an experiment that requires the shoulder of the 338 RUM to be pushed back about 0.175". I have tried:

a. a 325 WSM die (35 degree shoulder) and the case crumpled;

b. I annealed the shoulder area, tried "a." and it crumpled easier; and

c. I tried reducing it a bit with 300 Win Mag, then 30/06 and then 35 rem, which takes a long time and produces "steps" then "a.", and it crumpled.

Seems I need to reduce it in at least one stage before I can use the 325 WSM die, but problem is, "with what?". A 375 RUM, then 338 RUM?

Any ideas will be appreciated.

Is this new or fired brass? I find new brass is much friendlier in regards to setting back the shoulder, even friendlier than anealed fired brass. Once you fire brass and oringal slightly rounded shoulder transitions get "ironed" into the chamber, the brass is much tougher to fiddle with.

With a case as large in dia as the RUM, you'll need to push the shoulder back in stages. I'd say run the case through a 45 caliber die, then 40 cal, then 375 cal. then .338 die.

I dont know, but maybe a 404 Jeffery die-set will do it?

Thanks guys. Actually I woke up this morning with another answer and it worked.

Anneal the upper case and then run it into first a 8x50R (8mm Lebel) die, and then the 325 WSM. The 8mm Lebel has a wide base and a nice taper - and it's cheap to buy from Lee. Redding makes the 325 WSM die. It's an 8mm case I'm trying to form, hence the "8mm solution".

Fireforming will complete the operation.

Andy,
of course, sizing them out to straight and back down will work..

jeffe

Surprised to hear it took that much effort to find a solution, I take the 300 RSAUM and in one stroke with the big BMG press turn it into 300 WSSM with no failure, just a need to trim about 0.5" of the case ..... Imperial wax seems to make life a lot easier ...

So, whatcha up to?
Necking down to .308" and trimming to 300 Win length?

Just grind .175 off the base of a 338 RUM die and have at it.