The Heckler & Koch SL6 is a roller-delayed blowback operated sporting carbine made by Heckler & Koch. It is manufactured in 5.56x45mm NATO caliber. The design was originally based on the HK 630 sporting rifle and is essentially a shorter-barreled version of that rifle. It was marketed throughout the world as a hunting/utility rifle.
The roller-delayed blowback action is similar to that used in the G3 battle rifle and is the hallmark feature of HK's pre-G36 line of small arms. The four groove barrel features polygonal rifling with a right-hand twist of 1 in 10.6 inches. The chamber is fluted with 12 longitudinal flutes extending rearward from the baffle to the chamber face. These flutes permit propellant gases to flow around the case acting as a lubricant to ease extraction. Two rectangular recesses have been cut into the upper receiver to accept this mount.
The HK SL6 is no longer manufactured, having been replaced by the HK SLB 2000. The H&K SL7 is a variant chambered in 7.62x51mm NATO caliber.