sizing problems

[ishootkittens]

Just picked up my brand new 300 norma today and I had already purchased 338 norma brass and ran it through my sizing dies to make what I thought would work. None of my brass chambers. They are within the min-max trim range and now im assumimg either im doin something wrong or you cant form 300norma from 338 noma brass. Any clues?

 

[sable tireur]

ishootkittens,

Unfortunately, the .300 Norma Magnum is not a simple necking down of the .338 Norma Magnum case as you have already discovered.

While the two cases are similar the shoulder diameter of the .338 NM case is larger in diameter than that of the .300 NM case. That affects the case taper also. You need to get a dimension for the chamber neck diameter also to see if you need to do a little turning...

Both cartridges require their own unique headspace gauge also.

My guess is that you don't have enough sizing going on when using the standard sizing die for the .300 Norma Magnum case.

Regards.

 

[el matador]

Match grade chambers are usually pretty tight, so try adjusting your sizing die down until you get a firm cam-over. Going from a light cam-over to a very firm one will usually get you another .010" of shoulder bump. It's also possible that the sizing die is just too long, which would require removing some material from the bottom of the die or the top of the shell holder.

You could also try removing the expander ball and sizing a case to see if it's the neck causing the problem. Not very likely in my opinion, but easy to check.