Looking for some info on the optimum twist rate for a .260 Remington im having built for PRS/ long range coyote gun. I want to push the heavier 140’s possible some solids.
However, to fit in a mag with the 140 you will have to seat them into the case taking up powder column space and will lose some velocity. If you want to shoot a 140 and don't reload the 6.5 Creedmoor is the answer. If you DO reload 6.5x47 works REALLY well with a 140 Hybrid and 2750fps with Varget.
.260 and 6.5creed are almost identical ballistically. Same barrel length, same powder charge, same bullet, almost always gives the same MV +/- barrel variance.
At any rate, 1:8 is pretty standard for either. You won't need the 7.5 unless you're at really low altitude trying to push 147-155gr pills or something.
I'm building it on a LA receiver so bullet length will not be an issue.. I'm more interested in being able to shoot the 140's and up to the 150's+ and still be able to keep the speed up.
Back in the early 2000's, before the 142SMK, there was (and still is) a 140SMK, which is noticeably shorter. It would be my choice for loads which need to be mag fed.