Yup. 6 twist for the 30's, again, I have zip experience with the 6.5W but no doubt the same thinking I would guess applies from the 300
as to barrel length, I'm sure that would matter less vs. powder and where the speed of sound is at your place. Here its 930ish, my bud on the coast mentioned its 725fps
I'd think gray beards website, or the contender forum here will be loaded with info, contender shooters are fond of the round for silhouette
270REN another one to look at if you go contender
