I just looked through a bunch of barrels on line trying to decide on my next one which will be a 10.5" and I really had to dig to find the differences on some of them. On several, the only difference is gas port size. Just from one manufacturer, had 5 different 300 blackout barrels and all 10.5" and had 3 different gas port sizes to pick from. .072 .093 and .125 If I wasnt bored and really tried to figure out what the diff was I would have never known. Whatever I order will have the largest port I can get since Im going to put an adj gas block on it anyway. That may be the reason so many people have problems when they put one together.