I had a 30" Lilja 300 rum on a Ruger #1 with an 11 twist. As others have pretty much stated, you are probably on the "ragged edge". You can get by with a little less twist because of the high velocities you are probably getting, but anything over 210 is stretching it. It also depends more on the length of the bullet than the weight, so you may have a little wiggle room there. Unfortunately, the highest B.C. bullets are normally the longest ones.......Rich
I've got an 11 twist on my Broughton bbl in 300 RUM. It shoots the Berger 210 VLD accurately and has no problem with the 220 SMK either. The 240's probably need a 10 twist but they don't interest me anyway.