My M16A2 clone set up for CMP Service Rifle competition uses a correct round plastic handguard (with heat shields) that looks just like this, but it isn’t mounted on the gas block / front sight post. Instead I use a White Oak Armament free-float kit. I can rest the handguard on a support, or attach a taut sling and cuff, and nothing touches the barrel. That means repeatable consistency whether I’m standing, seated, prone, on a bench, bracing on a barrier, or whatever.