now,
im sure this question has been asked a thousand times,

im looking to get a re barrel for the ackley, i will only ever use between 68gn and 87gn bullets,

would the usual 1 in 10 twist be the way to go or would something different be the choice?

how many grooves?

thanks in advance

the 1:10 douglas barrel 243 ai I had would shoot about every thing up to 100gr.
check douglas site for the number of lands and grove. best groups were with barnes 87gr
and burger 95gr moly.
Lighter bullets liked imr4350 while the heavier bullets liked H4831Sc
Dave

The 6mm barrel with 1 in 14" twist can stabilize 75 gr Vmax [Length = .935"] out a certain range.

With muzzle 3200 fps to 3050 fps, it is very stable and accurate ~ 50 yards.

And then they keyhole at 100 yards 2850 fps.


87 gr Vmax are 1.037" in length.

http://kwk.us/twist.html

To get the right answer for the 75 gr Vmax, with that Greenhill calculator, you would need to enter an SG between 14.4 and 15.4.

Entering the 87 gr bullet length and our normalized SG, the twist would need to be 1 twist in 10.5" to stabilize down to 2000 fps.

And at 500 yards, I have killed a deer with less than 2000 fps terminal velocity.