Originally Posted by statjunk
I can't set the base of the bullet to the shoulder neck intersection because the neck on a 300 WM is smaller than the diameter of the bullet. It's approximately .2683". Short of the .308" theoretical min amount in the case.
Tom, I would talk to your smith and see what he recommends. From my recollection, the smith I used for my 300 WM suggested I set the junction of the boattail/shank to line up with the neck/shoulder junction, I think this is what Trueblue described. I couldn't do this due to magazine limitations. Anything deeper than this wouldn't increase the amount of neck contact but would help when you do start to get some erosion.
In my case, I didn't want to put in an extended mag box. My mag box was something like 3.590 max length so I set my OAL with the 180 AB at 3.500. I had the throat set to seat at -.020. With this arrangement, I picked up a fair amount of case capacity, it feeds nice, I don't have to worry about recoil on rounds in the mag, and I have extra room to follow the throat if it starts to erode.
Not sure if this helps with the info you're looking for, but hope it does.