Go to richards stocks in VA. H advertises on www.6mmbr.com
He is shooting exactly what you are talking about. it is a 300 WSM
shooting the 125 Btips at around 4000 fps. I think he is using a 15 twist.
A cut rifled barrel mftr can make any twist.
The 30 BRs are shooting 17 twist with the 118 FB bullet and 115/16 twist with the 125s. However you cannot go by that. The FB tend to go one twist slower than the boattail.
I have a 17 twist Kostyshen barrel with 118 BIBs and it is a one holer at 100.