How to Customize Equipment on the HK 91

The HK 91 is a precursor to the HK G3. The German company Heckler and Koch manufactured 91s in the 1980s and G3s in the 1990s. The G3/91 platform is now discontinued. In the 1950s, Heckler and Koch designed what would later become the model 91 and later the ubiquitous G3, which is still in military service today in the 7.62x51 NATO caliber. The HK 91 is a versatile firearm. You can customize it in a variety of ways without the help of a gunsmith, but using a gunsmith offers many more possibilities.

Things You'll Need

  • Picatinny rail
  • EOTech, Aimpoint, or Trijicon sight systems
  • Dedicated ammunition
  • Claw mounts
  • Zeiss optics
  • Conversion kits
  • Armorer's tool
  • PSG-1 trigger group
  • Foregrip handles
  • Rail-mounted weapons
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Instructions

    • 1

      Discern whether you have a picatinny rail on the top of the 91. In order to add custom components, this rail must run the length of the upper receiver and meet the stock. The picatinny rail will look like a grooved piece of metal screwed into the top of the receiver. If your gun does not come with the rail system, applying parts will become very difficult if not impossible.

    • 2

      Procure the HK claw mount by ordering them at your local gun shop or off the internet. This claw will serve as the base for your choice of a traditional optic, allowing you to mount it without drilling or tapping the receiver.

    • 3

      Mount an optic according to the chosen optic's instruction manual. Zeiss optics are generally considered to work well with HK mounting systems.

    • 4

      Have a gunsmith attach the picatinny rail to the 91 if you decide to use red dot or holographic optics from EOTech, Aimpoint or Trijicon.

    • 5

      Slide the forestock handle and your choice of rail-mounted weapon on the picatinny rail. Adding elements to the rail is very simple--just align the opening in the grip and weapon with the rail, and slide the element along the rail to the desired position. Once the desired position is attained, screw down the element for a secure fit. The rail-mounted element will come with additional instructions.

    • 6

      Have a gunsmith replace your standard trigger group with a PGS-1 trigger group if you want a heavily modified look or you are using the 91 for dedicated marksmanship.

    • 7

      Convert your 91 with the help of a gunsmith to 7.62x39 or .22 caliber.