I have limited experience (I worked with 1 rifle in .22-250 AI) with this topic but can offer some insight. I put a 1-8 twist Shilen on a Mod 70 push feed after scorching the throat on the factory tube. It was 26 inches long and I was able to push 75 A-maxes to 3400 fps easily with Re15. It would shoot 1.25 inch 5 shot 100 yrd groups, but really shined out at 300 and beyond, going well under MOA at extended ranges. Never shot it at 1000 yards, but sold it to a friend who punches paper at that range and he says it does well. I put together a .22-6mm Rem AI on a long action push feed Mod 70 with a 1-7 twist 28 inch tube and shoot 80 gr Berger VLD's at 3550 fps. It made the .22-250 AI expendable.
ED