Other than feel (better swing on longer vs. quick point on shorter) and special purpose, (e.g. trap better with longer), can anyone offer an explanation of the different effects of barrel length? My understanding is there is no difference in velocity and the shot pattern is governed by the choke, naturally. But there is flatness to the pattern at certain distances? Optimal length for certain loads? Therefore, what other physics does one need to know regarding barrel lengths? Thanks.