One more point - on twist, I have a copy and perhaps the actual Handloaders digest from late 60s or early 70s, author not sure, may be Robert Sherwood, did extensive test on 6.5x55, used newspaper/phone books or something like that for media.
He tested 6.5x55, and also 6.5 Rem Mag, it seemed to show more bullet upset (same bullet in each rifle) at a lower speed in the Swede, his theory, faster twist rate made a difference, not great, but noticeable.
Debates I have concluded on twist rate is that it's perhaps more 'academic' when it comes to killing effect. I Do always choose a faster for cal spin and never the slowish side as some opt for optimal accuracy.
MY thoughts on twist, the faster twist rifles all else equal give a great opportunity for the bullet to maintain nose forward throughout penetration in an animal - perhaps maximizing the opportunity for straight line penetration. Also, there may be some benefit if a bullet hits brush, that if faster spun, having less chance to stray off course. My theories not tested, but I feel there may be some benefit here.
That said, my 270/150 PT kill, the Partition lost the front half core ROTATED base forward the last foot or so of penetration and the jacket after parachuting open had closed back up once it went into base forward mode. No big deal, nearly exited the Mulie from 275 yds, neck to ham. Perhap a 140 PT from an 8 twist Swede would have punched thru, needless to say, that buck only managed to drag itself perhaps 30 yds in the snow, after dropping at the shot.
