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. The one other modification H&K made for the HK43s was to mill off the trip ledge on the bolt carrier assembly. Moreover, the grip frame housing was modified to prevent the selector lever from going into the full-auto position. The auto-sear was removed from the fire control group, as well as the trip lever, to prevent automatic fire.

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 HK43, which was the precursor to the HK91, was for the most part identical in appearance to the HK33. Of the approximately 377 HK43s produced, it is estimated that about 200 were imported into the U.S in 1974. HK43s were sold with 25 round steel magazines. 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. In 1974, a semi-automatic version of the HK33 was introduced by H&K and was designated the HK43. 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 Heckler and Koch HK91 is a semi-automatic battle rifle based upon the Heckler & Koch HK33 assault rifle and is the follow-up to the HK43 rifle.

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