I think the Marlins have a 1 in 20 twist. I have seen a few with slower twist as well. 300 Grain is the lightest jacketed bullets I have seen. There are some cast bullets in the 275-285 grain range. I spend the most time shooting the NEF rifle. In this caliber the NEF is really accurate. As is the 223. Accuracy is pretty good in all calibers for a 200.00 rifle. With my bad shoulder, I have a little trouble with levers except for the Brownings. On second thought Barnes makes the 250 grain X Flat nose in 45-70.