I have two 260's, one a rifle I use in F class competition with the 142 MatchKing, the other one I use for hunting. Both rifles were built with 1 in 8 twist Krieger barrels. Two friends of mine have 260 A.I.'s and that they really like as well. I think you be hard pressed to find a medium capacity case that will do what the 260 will do.
I feel the 1 in 8 twist is perfect for the 260 Rem or the A.I. version. While I have shot nothing but the 142's thru my match rifle, I have shot bullets as light as 90 gr. (Speer TNT) up to the 140 gr. Sierra SBT GameKing thru my hunting 260 with excellent results. So the 1 in 8 twist will be fine.
Velocity, from my friends 260 A.I.'s the "accurate velocity" with the 140 gr. class bullets seems to be around 2850 fps. Velocities in the low 2900's are possible but the real accuracy, like I said before, is at 2850 fps in both of their rifles. This is + or - 100 fps over the "accurate velocity for a standard 260 with a 140 gr. class bullet.
Since I am assuming you will be using your 260 A.I. for hunting mostly, listed below are the accurate velocities for different bullet weights from the 24" Krieger barrel on the standard 260 hunting rilfe. As a minimum you can expect at least that much velocity.
90 gr. Speer TNT: 3465 avg. fps. with IMR 4064. This load load blows windows through coyotes. Definetly not a fur bullet.
120 gr. Sierra Pro Hunter: 3007 avg. fps again with IMR 4064. This load has performed excellent on deer.
140 gr. Sierra SBT GameKing: 2745 fps with
H430 EXT. I have used this bullet on feral hogs with excellent results. Complete penetration and dead right there hogs.
Accuracy with all the above bulles from the 1 in 8 twist averages .5 MOA or less. The loads I shoot came right out of the Sierra 5th edition manual. Again, I think you could expect around 100 pfs more accurate velocity with the above bullets with A.I. version. I would use nothing shorter than a 24" barrel if I were you.
Hope this has helped some.
RiverRat
