Either 1-12 or 1-14. A 1-14 will stabalize evertything 250 gr and under, and is a bit friendlier for cast bullets. It'll also stabalize the lyman 3589 ~280 gr cast bullet just fine.
Remington went with a 1-16 twist that is marginal for 250 gr bullets.
My 35 whelen acklety (now a 350 Rigby) was/is 1-14, my 350 rem mag is 1-12, both will put 3 shots well under 1"
