Butch,
two things, Rem builds a factory 300SAUM and I have built one from a normal short action 700. Is the tenon the same thread diameter as a factory Rem? If so I would not be concerned.
Bill

Thanks Pat. How is the house coming? How has your hunting been so far? I will see you at the matches next year. Bill, thanks for the reply. I have old friends from Alaska that moved to Ballground several years ago, Jeff and Sandy Schaefer. They use to have a pretty large construction company. Haven't heard from them lately. Butch

The Rem 700 tenon is 1 1/16" diameter. The Winchester M70 is 1" and is offered in the WSM which is fatter than the SAUM series. The Browning A-bolt is smaller yet.
The Savage in WSM is 1 1/8. This was probably to increase the size of the barrel ahead of the receiver rather than the tenon itself.
The 1" diameter of the Winchester has been shown to be problematic due to receiver construction (incomplete threads)and poor fit of the threads. With a good thread fit there would probably be little problem with it. Regards, Bill.

Thanks for the reply Bill. I have ordered the reamer and headspace guage from Dave Kiff. The Jewell trigger just hit the door yesterday. The Shilen 12 twist #5 contour should hit in the next two weeks. I need to make a decision on a stock and am leaning towards Remington's box magazine. Is Brownells the best source for that? Butch