I have a 6.5CM in the Predator line of Ruger American that shows promise. Only have one quick range session but under an inch with no real break in. I think it'll tighten up with 50 or so shots on a factory barrel that's not hand lapped.
I have 2 friends with the standard .243, and neither had good success with that specific rifle. Not saying all are bad, but neither of theirs are shooters so far. One tried hand loads and factory, one just factory.
Overall for the money, I'm pleased with my Predator model. I cleaned up the barrel channel and worked over the trigger myself, and it's like a new gun. Perhaps see if they offer a .243 in the Predator line with a little beefier barrel?
Good luck.