So i want to build 9mm upper for my SBR lower. Quetion is what barrel length. Id like to have about a 5" barrel with my ti-tant can under a 9" handguard. Ths would be the "fun" configuration. But i realize I cant run it surpressed in PCC so what can I thread on the barrel to get the gasses out past by handguard if the barrel is 3.5" or so shorter? Is there any reason i cant envision why id want a longer barrel say 8" on a seven inche handguard for PCC. Bummer is then with the can I'm 14.5" 15" long which negates the "fun" facror plus the can doesnt look as good sticking out there by itself.