Some initial work with my Hart 14 Twist with .030 freebore-24"
60g Sierra, Rem 9 1/2
39.0g of AA2230-3870 fps
39.5g -3919
40.0g -3950
40.5g -3978-No pressure on this load, primer still round
55g Nosler Varm, Rem 9 1/2, AA2230
39.0g-3967
39.5g-3979
40.0g-4053
40.5g-4089
41.0g-4096-No pressure on this load
55g Nosler ballistic tip, is more accurate shooting in the 2s at 41.0g at 4096 fps, but I spend little to no time in a load tune, and AA2230 was the only powder I worked with.
These beat 243 Win loads in speed in barrel lengths the same length.
Two friends here are killing a lot of deer with the 70g Nosler ballistic tip...who in the world would have thought of that combo?
In my 8 twist, 87g through 108 shot extremely well, but with the .160 Freebore I put in the chamber, 70s did not shoot tiny groups, but good enough to kill a coyote with. In the 8 Twist, I would start with an 87g bullet at the lightest, but an 80g Berger may work very well, if you can find any.
Years ago, I killed a lot of coyotes with the 60g Sierra in a 243 Win and 6 Rem when I was hunting in Mexico, one heck of a bullet. Also, the 80g Sierra Blitz is a superb coyote bullet, and you hear the extremely loud PLOP sound every time you hit one!
In this particular 24" Hart, 14T, .030 freebore, the 70g tnt and Nosler ballistic tips are shooting in the very low 2's at 3740 fps, this is one heck of a coyote load, and with a few of the 75g Hornady V max, it was super accurate at 3690 fps, not playing with but one powder, AA2230.
A 26" barrel, 14-12 twist, .030-.050 Freebore would be pushing the 70s at or close to 3800 at the accuracy node. Speed kills.
Faster twist, more freebore may bleed off some speed, but you do not know till you try, Best Wishes!
Tubbs Brass is incredible in how tough it is, even with the large primer pockets.
Dave Aflac made some videos of shooting rock chucks with the 75g V max with a muzzle velocity of 3800, shot out of a 6 Rem AI. The chucks were launched 15 YARDS in some cases. The 6 XC with a Long barrel would be in that neighborhood, and a 29" 12 Twist with 75 Grain V max would make a very, very impressive chuck/p. dog rifle that would equal my 243 AI in performance with a LOT less powder.