All told I don’t have any rifles chambered with an Ackley chamber because it’s not worth the extra effort.
Some of the older/tapered cases (250Savage Improved, 257 Roberts Improved, 30-30AI) see a good increase, but the 243 has a modern case shape.
THIS!
You Nailed it SuperCub. That's about the best explanation I've heard. I have one AI and that's a .257 Roberts. I went with the .257 because for years I always heard the .257 showed good gains. However, one thing puzzles me. The .30-06 case is old fashion also, but the AIs I've read about it were minimul of any gain which leads me to believe there are other factors involved. Maybe amount of overbore has something to do with it.
My .257 shows gains with 115 grain bullets of up to 200-300 FPS over the standard .257 Roberts depending on propellant used. I've had the best gains with the 115 grain bullets using RL-17. However YMMV.
