You will problaby find as much accuray variation among different bullets of the same diameter, as you will among varying diameters. Goove diameter in the .45 ACP can run from .450-.451+, and it is often believed that cast bullets work best .001" over groove diameter. So, you are fine with .451"-.452" bullets. The Hensley & Gibbs #68, a 200gr. SWC, is probably the most widely used cast bullet for the .45 ACP. Most companies selling cast bullets will have a bullet either dropped from that mold, or one very much like it. You can't really have a flat trajectory and low recoil, but to 25 yards, you don't have to worry about bullet drop. If you are going to be shooting out to 75 yards, then you'll have to push the bullet, regardless of weight, at fairly high velocities, if you want it to shoot flat. On the range, where distance to target is known, flatness of trajectory doesn't matter, you adjust your sights to suit. There you can load soft. In the field, if you want flat trajectory out past 50 yards, you'll have to load faster. A 200 gr. bullet at 850fps might be a good compromise. Of course, for strictly range use, 750 is plenty, and for field use, 950 would be better. SWCs poke nice holes in paper, and are pretty good as a hunting round. I think the Nosler 185 JHP is used by some as a strictly paper-punching round, as it is extremely accurate. Some guns have problems feeding SWCs, but you won't know until you try.