I have a 12 FV in .223 (1in9 twist) that will shoot 69 SMK's but will not stabilize heavier bullets (i.e. 75 A-Max). If I rechamber this barrel to 22-250, will the heavier bullets stabilize due to higher velocity/revolution? Would another chambering work better?

I want to do something to this barrel because it just isn't as accurate as I would like it to be (no better than 3/4" @ 100 yards, usually closer to 1").