I have a .338-06 that I have a bunch of silver plated brass for that I want to neck down to 8mm-06. I replaced all my .338-06 brass with properly headstamped Norma brass so I have the stuff just lying around. I figure if I use the silver brass on my 8mm-06 it will help to keep it from getting mixed up with my .30-06.

I necked it down in the full length 8mm-06 RCBS die, reloaded and seated 175 grain Sierra bullets. The problem I'm having is the crimp isn't holding the bullet during recoil of the rifle. Do I need to neck these all the way down to .30-06 and then go back up to 8mm? What might be causing this problem? Will a Lee crimp die help with this problem and if so will an 8x57 die work with the 8mm-06?

It should be unnecessary to crimp a cartridge like the 8mm/06 in order for the bullets to be held firmly in the cases.

The nickel-plated cases do have a little more "springback" than unplated cases, but I would doubt enough that it would cause lack of bullet tension. At least, the .308 nickel cases I have necked to .243 do not exhibit this tendency.

However, the one way to achieve the tension you want is to reduce the size of your expander button. You can do this by chucking it in a drill and polishing with emory cloth.

I had a 300WSM Redding F/L sizing die that was machined incorrectly and the cases wouldn't hold tension on the bullets. This may be the problem you are having. Redding sent me a new die and it fixed the problem.

I bought a set of RCBS 8X57 dies used about 20 years ago. The expander was about .3225. It left the necks too loose. I bought another expander and kept the original for cast bullets.