Originally Posted by WisconSniper
And what about using a 300 Norma Mag as a parent, necked to 6.5?
Are you talking about the .308 Norma Mag or a cartridge based on the .338 Norma case?
What, exactly, are you trying to accomplish?
I don't know much about either cartridge. The .308 Norma Mag is similar to the .300 Win Mag, so you will just end up with the .264 Win Mag.
The .338 Norma Mag case is a beltless case that is just a bit shorter than the .338 Lapua case and has a bit less case capacity.
Keep in mind that the real performance limitation with big cased 6.5's is the lack of powders with the correct burn rate to get optimum performance from their overbore capacity. The .264WM generally tends to do its best work with Retumbo, which is one of the slowest powders around. RL-33 may prove to be better yet. When you step up in case capacity from here, there isn't another class of suitable powders to step up to, which really limits the velocity gain from the increase in case capacity.
You could step up to a 6.5 Shooting Times Westerner and gain some velocity or accomplish pretty much the same thing with a 6.5/.375 Ruger. Over and above that, you are going to gain very little vs the powder you are burning.