Al in Mi wrote:hoot, and difference in case capacity?
Did some more lathe work. With the neck opened up with a letter "N" drill (.3020) but not yet fireformed, the wall was .017. Factory cases average .015. Important point: This was measured with a digital caliper, not an appropriate case neck micrometer. Anyway, with .017 wall neck, the sized 450b case capacity again not fireformed yet, was 43.3gr of water. Unfired factory 30RAR cases measure 43.7gr and fireformed resized factory case read 44.3gr. So we're in the ballpark.
Dialing in the case with an independent 4-jaw lathe head is a little slower that I would like to do it, so if one was going to consider this seriously, it would be a good move to get an actual neck reamer setup, or at the least fabricate a QR case holder to chuck in the lathe. Getting the correct sized custom reamer would be a good move as well, though the letter N drill is darn close. Good luck finding a shell holder for an RCBS trim-pro.
Again, this segue was out of curiosity. We're not hurting for brass that badly yet.
Edit: Turns out I forgot to deburr the mouth. Having done that, the 450b case neck wall was .015, just like the factory 30RAR cases. What's the odds of that happening? Oh yes, the case chambers fine in the rifle. Satan, get thee behind me!