Everything that makes the BRN-180 300 Blackout great, with enhanced features for suppressor use. With the BRN-180S 300 Blackout being frequently used in conjunction with suppressors, Brownells sought out new features that make the platform quieter and better to use with a suppressor. Still mounting to any standard AR-15 spec lower receiver, the new BRN-180SH Suppressor Optimized Upper Receiver notably includes a gas shutoff setting. This is not uncommon on piston driven firearms, it has rarely been utilized as a true "single shot" setting. Combined with the adjustable charging handle, which can be pointed downwards like a bolt action, the BRN-180SH can be configured into Mfg: Brownells