Quote: "4" barrel vs. 4.5" barrel (.45) "
Are you referring to revolvers or 1911's? I'm not aware of any 1911s with 4.5" barrels. There are 3", 4", 4 1/4", 5", and 6". My 4" and 5" Wilsons shoot equally well at 18 yds. The main difference between 4" and 4 1/4" guns is that the 4" guns are frequently bushingless bull barrels and the 4 1/4" guns have standard barrels with bushings. IMO, any difference in accuracy between the two barrel types/sizes would just be the normal difference from one pistol to another.