HK91

The Heckler and Koch HK91 is a semi-automatic rifle based upon the Heckler & Koch HK33 assault rifle and is the follow-up to the HK43 rifle. John Matrix retrieved an HK91 from his personal weapons shed and uses it to kill Diaz, but it is taken from his daughter's kidnappers before it can be used further.

Overview
In the mid to late 1960s, Heckler & Koch developed the HK33, which was a scaled down version of the Heckler & Koch G3, but chambered for 5.56x45mm NATO. The HK33 entered production in 1968. In 1974, a semi-automatic version of the HK33 was introduced by H&K and was designated the HK43. According to H&K’s numbering nomenclature, the “4” indicates that the weapon is a paramilitary rifle, and the “3” indicates that the caliber is .223. HK43s were sold with 25 round steel magazines. Of the approximately 377 HK43s produced, it is estimated that about 200 were imported into the U.S in 1974.

Design
The HK43, which was the precursor to the HK91, was for the most part identical in appearance to the HK33. Instead of a “push-pin” grip housing, it came with a clip-on style grip housing marked “SF.” In order to save money, H&K used the same fire control group that went into the HK33 models, but with some modifications. The auto-sear was removed from the fire control group, as well as the trip lever, to prevent automatic fire. Moreover, the grip frame housing was modified to prevent the selector lever from going into the full-auto position. The one other modification H&K made for the HK43s was to mill off the trip ledge on the bolt carrier assembly. Early HK43s were made from the same barrels used on the HK33 rifles, which were 15.35 inches in length and had a 1 in 12-inch twist. In order to bring the barrels up to the legal length of at least 16 inches in the United States, a flash suppressor, which adds about 1 3/8 inches to the overall length, had to be permanently attached. H&K also omitted the grenade launching snap rings on the barrel, as they had for their HK41 models, because the Gun Control Act of 1968 prohibited such features on imported rifles. The HK43 also lacked the "flapper" or paddle magazine release making the redundant push-button magazine release, located on the right side of the receiver, the only way to eject a magazine. Like the Heckler & Koch HK41, the HK43 had a NATO black finish, which differed from the black phosphate or blue-gray finish of the later HK91/93 series, and came with a short slim forearm grip. Moreover, there were no proof marks on the receiver. Only the rifle’s model and serial numbers, as well as date of manufacture were engraved on the left side of the receiver. The date code indicated the month and year the rifle was produced. The HK43 was also fitted with an all-plastic MP5 style butt stock with the recoil buffer attached to the bolt carrier.