Re: 222 Max distance
I had a 222 recut to 223. I ended up selling it to a friend, several years later I've got it back, he felt it didn't shoot very well. I couldn't remember it shooting as bad he was getting. It finally occurred to me it was a 1-14' twist. It doesn't like the newer, longer bullets even in the 55-60 grain range, but the 40-45 grains are great. I think I'll go down farther in weight to the 36 grain Varmint grenade, try to keep the splat factor up. I'm unsure what that will be but 200-250 yards doesn't seem unreasonable.
I can't say how that affects your particular situation, but I think a 4-12 would do most of what you want to do with a .222 or .223. I don't feel handicapped with a 2.5-8x.