The Heckler & Koch SL8 is a semi-automatic rifle manufactured by Heckler & Koch. It is the civilian version of the Heckler & Koch G36. The rifle fires the .223 Remington or 5.56×45mm NATO cartridge and feeds from a 10-, 20- or 30-round detachable magazine (depending on the variant of the rifle). Unlike earlier types of HK rifles, it is not a roller lock bolt but rather a lug-type rotating bolt system as seen on the AR-18. Design To adapt the G36 for the civilian market, its pistol grip and folding stock have been replaced by a fixed stock with a thumbhole. The receiver has also been modified to prevent the attachment of a folding stock. In addition, to comply with the Gun Control Act of 1968, SL8 rifles exported to the United States have been modified so that they will not accept staggered 20- and 30-round G36 magazines, only accepting single stack, 10-round magazines. Other modifications have been made to the SL8, including a lightened trigger pull, adjustable cheekpiece and buttplate to customize the fit to the user, and a heavier, more accurate barrel. The SL8 does not come with the carry handle and built-in optics of the G36, although these can be purchased aftermarket and fitted to the weapon. American owners can modify their SL8s to accept 30-round G36 magazines and 100-round drum magazines. Doing so requires that the single-lug SL8 bolt head is replaced with a double-lug G36 bolt head, the magazine well is replaced, and the receiver is modified to permit insertion of a wider magazine body. However, such modifications to SL8 rifles (or indeed to any imported rifles) have significant implications under the 1968 Gun Control Act, which prohibits (inter alia) the assembly from imported parts of rifles that could not themselves be imported. Variants SL8 (no -#) This is the grey EU and Canada version that has a double-stack magazine, non-vented forearm and a short sight rail. SL8-1 The SL8-1 is the grey US-import version of the rifle. It has a single-stack magazine and its sighting system consists of a long rail with ironsights. The bolt is slightly modified to accommodate the single-stack magazine. The forearm is not vented. SL8-2 Very rare, this version was designed as the new DMR for the German Bundeswehr, although in the end it was not adopted. It was to be issued with bipod and G36 type 3.5× optic.