I don't believe that's exactly true. It depends on the percentage of constriction. .650 in a ber/Ben threaded gun is TOTALLY different than say an invector plus & the reason is that the bore diameters are totally different. I wouldn't hesitate to shoot mag blend through a supernova (uses ber/Ben chokes) using a .650 because the bore diameter is already smaller.....but the bore diameter is larger in an invector plus gun .....so a .650 would be super,super tight. What kind of gun is it?