honestly not enough to notice just my 2 cents. in some cases ive seen a shorter barrel hit a higher velocity then a longer barrel with the same load velocity also has alot to do with many other variables that are more prominant thatn barrel length like bullet constricity in the bore, twist rates and powder burn rates. with new technologies and better proppellents these days worrying about barrel length is a bit old old fashioned unless we are talking barrel lengths under 20 inches. I honestly wouldnt worry about it