243 no doubt! My 243 AI, I take during deer season. Kills deer DRT and not as hard on fur as my 300 WM if I get a shot at a coyote lol
I’m a huge 6mm fan. I’ve built and owned them all. 6mm-06 AI, 6mm and 6mm AI, 6x47 lapua, 240 Gibbs. The works.
If I had to only have one, it’d be the 243 AI. No doubt. You can find and shoot factory ammo if you’re in a pinch and need some. And on top of that, fireforming brass is as easy as just shooting factories.
It by no means has to be the Ackley version. If you reload than you’ll reap the benefits. Otherwise the smoke bone stock 243 will do all you’ll need!