I've had 1X9 barrels shoot 77 gr. Bullets very accurately. I've had 1X7 barrels that did very well will 55 gr. Bullets that wouldn't shoot heavies worth a damn. I've got a 1X9 barrel that incredibly accurate with Sierra 69 gr bullets 1.5" groups at 200, but won't group 68 gr. Hornady at all....to the tune of 6-8" at 200. I would hesitate to buy a lot of any bullet, until I had a good idea of what my barrel likes! And I would shy away from selecting ammunition based on twist rate.