After a bunch of reading, gnashing of teeth, flip flopping,hand wringing, and generally being confused I've settled on 6.5 as my next rifle (I already have 2 .308 rifles, one bolt one gas.) Playing with the Berger twist calculator it's showing 1-7 or 1-7.5 seems to give a little more stability to the 120-140 grain rounds, but so far everything I've seen and without going full on custom 1-8 seems to be the standard. So what I keep looking at is a Bartlein M24/40 contour 1-8 twist 27 or 28 finished length. That should give me the widest range of ammo and the quickest turn around since I've found a few in stock.

Thanks.

1/8 will be fine.  I have a Krieger 1/8.5 and it shoots 140 grain bullets in the same hole at 100 yards  and I have hit 8 inch gongs at 1000 yards so its GTG at least for me.

1/8 works fine for me.

sorta

what litz is saying isn't that 8 twist won't keep it from keyholing, but rather at that stability factor, the BC isn't quite as high as if it were optimally stable.  and possibly there will also be a difference as the bullet goes transonic.   so he provides a correction factor in that calculator.

i shot 140 VLD and later 140 hybrids for many years with an 8.5 twist and it was super accurate and never had any stability problems.   later, i tried a gain twist that took me all the way down to 7.4 and i couldn't tell any difference in the BC or data at long range.  i've been shooting 8 twists for past couple of years but not for any particular reason.

I go with a 1/8 twist on all my 6.5s, and prefer ~140 gr bullets. But I'll be trying some 135 gr. Bergers this next year..