I'm having a 375 Whelen AI built now and am wondering how folks form brass for the round. 35 Whelen brass makes the most sense but the distance from the case head to shoulder is shorter on the whelen than on the standard 30-05 case. Is the 375 Whelen based on the 30-06 shoulder location or the 35 Whelen? If its based on the Whelen, will I have to neck beyond 375 and create a false shoulder for the case to headspace on while forming brass? Does anyone know where I could find chamber drawings? Thanks!

Good place to start is Clymer.

http://www.clymertool.com

They show their dimensions under reamer design.

The outside shoulder of the Whelen and 06 are at the same spot. The neck will hit the shoulder at a different spot because of the diameter difference. You can take either the 06 or 35 Whelen brass to start. I would use the 35 less distance to go. If you load the case and it is not a crush fit in your chamber then either set the bullet into the lands or add a false shoulder.

Ramrod, thanks for the link. Some quick calculations--
If the brass is the same thickness at the shoulder as at the mouth (I know it tends to be thicker at the shoulder), 06 brass whould have an inside diameter of around .4101 at the shoulder. A 416 expander (.414 nominal) would expand the shoulder about .01. I assume that running the straightened case into the 375 whelen ai die would resize this portion of the case as the false shoulder should be formed very near the original case shoulder, right??

Can anyone avise me as to how a case should be annealed when doing a fairly radical neck up? Would a slow cooling rather than the standard water quench make for softer brass--then re-anneal following the neck up in the standatd fasion to return the brass to a more standatd hardness? I'm just thinking out loud here.

I have heard that the Rem brass is thicker and I want to preserve case capacity for this round---the differecne may not be enough to matter though.

Thanks!