I have a 6 mm AI built on a Remington 243 barrel that is a 1 in 9. It shoots 100 gr bullets at 3,300 fps with a case full of Re22. Never tried anything heavier. It’s a sub inch rifle built on a 1942 Oberndorf build 98 Mauser. 7828, VV N-165, and H 4831also worked pretty well but Re22 was the best in my rifle.