HK 91/G3 Overview

Learn about this iconic rifle:

The Heckler & Koch G3 is a rugged 7.62×51mm NATO battle-rifle built on a proven roller-delayed blowback system — a workhorse adopted worldwide, known for simple, reliable mechanics, modularity, and legendary military pedigree.

The HK91 variant is the semi-automatic version that has been converted from the G3 platform.

Specs:

• Caliber: 7.62×51mm NATO (standard).
• Operating system: Roller-delayed blowback.
• Standard barrel lengths: ~16.5–20” variants; standard G3 ~17.7” (varies by model).
• Feed: 20-round steel or aluminum box magazine (also 50-round drum options and many aftermarket mags).
• Weight (unloaded): ~4.1–4.4 kg (varies by variant).
• Rate of fire (original full-auto): ≈500–600 rpm.
• Primary users/adoptions: >70 countries; produced under license in many nations, most notably FMP (Portuguese).

Variants of this platform:

• G3A3 / G3A4  standard military field models (A3 = fixed stock + wooden/polymer handguard; A4 = with scope rail).
• G3K / G3KA4 carbine/short variants (K = kurz / short).
• G3SG1 / PSG1 sniper/precision derivatives built on the G3 family (PSG1 is famous, high-precision HK variant).
• HK91 / HK911 semi-automatic/civilian export variants; imported to the U.S. in the 1970s–1980s with compliance modifications (HK91 importation ended around 1989; roughly 48,000 imported historically).

Why you should choose this platform:

• Proven battlefield durability: decades of service across climates and armies.
• Simplicity & reliability: roller system is robust and forgiving.
• Powerful cartridge: 7.62 NATO gives strong terminal performance and long-range capability.
• Parts & aftermarket: large ecosystem (magazines, stocks, rails, optics adapters, triggers PSG1 parts).
• Modularity: readily adapted to optics, modern stocks, and accessory rails (many users modernize with HK-pattern rail adapters).

Common upgrades and accessories:

• Optics rail conversions / scope mounts: most sellers fit Picatinny or HK-style (style or specific?) rails or LMT / HK-style scopes (A4 receivers commonly already have rails). PSG1 rails and Hensoldt optics are classic premium options.
• Furniture swaps: modern polymer adjustable stocks, pistol shock-absorbing grips, and free-float handguards can reduce weight and improve ergonomics.
• Match barrels / triggers: precision barrels and tuned triggers (or PSG1 components) for buyers seeking marksman performance.
• Suppressor & muzzle devices: many use muzzle adapters or flash hiders for suppressor compatibility (legal region dependent).

Upgrade your HK91 / G3 with our top five must have parts!

1. HK91, G3, and PTR Sniper Match Trigger Group

The HKP match trigger group starts life as a standard 12lb stock trigger pack before being carefully converted by the legendary trigger gunsmith, Bill Springfield.  The result, a smooth and crisp 5-6lb pull with reduced trigger slack and over-travel.

HK91, G3 Match Trigger Group - Sniper

2. HK G3 & HK 91 4 Position (0,1,3, F) Burst Trigger Group Complete - New Factory German

The look and feel of the original 4-position, push-pin trigger group but with a semi-auto trigger pack. This clipped and pinned housing is drop-in ready and a great upgrade for your HK or PTR91 rifle.

HK91, G3 Trigger Group - 4 Position 0,1,3,F - Safe Semi Only

3. HK91, G3 Retractable Stock - MKE

The MKE retractable G3 Buttstock is an easy-to-install replacement stock system for HK G3-style firearms. The simple lock/release system is easy to operate, allowing shooters to quickly adjust stock length. Steel rails and components offer superior strength and stability, while the non-slip rubberized buttpad absorbs recoil to reduce shoulder fatigue. 

HK91, G3 Telescopic Stock

4. HK91, G3 M-LOK Handguard

The HKP M-LOK tactical handguard installs easily to provide a solid base to mount M-LOK accessories. Designed from the ground up by HK enthusiasts with tactical shooting requirements in mind. 

HK91, G3 Handguard - M-LOK

5. HKP HK91, G3 50 Round Drum

Modeled after the discontinued HK G8 50 round drum, the HK Parts drum steps in where the original left off.  Each drum is crafted in the US from billet aluminum with aluminum and steel internal components for a lifetime of use.  Our drum is simple to load and feeds reliably in all weapons listed in the compatibility section below.  

HK91, G3, PSG1, HK11 Magazine - 50 Round Drum