The word "any" means the same as "no loss" in this usage. You will always gain speed with a longer barrel, at least, until you get to the point where the pressure in the barrel is less than the loss due to friction. That is probably well over 30 inches in a 6BR. Jackie Schmidt did some testing for 6mmBR.com. Read that.My Barrel will be big and heavy, so i want to keep it as short as possible without sacrificing any speed.
yes there will be less flex or whip with a shorter and or fatter barrel. the bullet is pretty much up to speed at 24 inches ,after that you will loose about 8-10 fps per inch .the larger loss would apply at 24 to 16 inches area of the barrel.hope this helps sir. tim in tx