About twenty years ago, I chambered two 6mm AI's, both single shots. At the same time, I built myself a 6mm Remington, based on a pre-64 action. All were eight inch twist barrels. They were thinking they would be able to push 198's to over 3200 fps. They did manage to achieve 3200, but that was it. My 6mm topped out at 3150 fps. I should mention, barrel life sucked! Interestingly enough, at the same time, I built a 6BR for myself, on another Winchester action. With the little 6BR, I was able to achieve 2990 fps (26 inch barrel) with the same bullet. It shot better too.
If I was to build another 6mm today, I would likely go with a 6mm Creedmoor. I could match the 6BR at lower pressure, and should get better barrel life than the Remington. GD
