I run a 4.5 inch barrel but have a 10 inch handguard. It runs suppressed 100% of the time Bc of it. I’ve had 7.5-9 inch handguards on it before and even a faux suppressor when my suppressor was used on other guns. But I have since switched it to 3 lug and bought a suppressor to use on all my 3 lug guns.