I have some cheap bevel base 300 gr rnfp for that I picked up when I first got into reloading and not knowing any better. I never have been able to get these to shoot well in my guide gun. As proof of concept, I have sized these down to .452. I used a Lee .454 first the a Lee .452 push through die. I had intentions of trying these out in my .454 over Trailboss, but have never gotten around to it.

I have heard of people sizing jacked .310 rifle bullets and .312 pistol bullets down to .308 to shoot out of things like .300BO and .30 Carbine, but have never done such myself.