AR-15 vs Heckler & Koch HK91

1964–Present

1977–2000

12,000,000+ units (combined military, law‑enforcement, and civilian production)

~250,000 estimated

840 mm (33.1 in) with stock extended (16 in barrel), 730 mm (28.7 in) with stock collapsed (14.5 in barrel)

1,020 mm (40.2 in) with stock extended

406 mm (16 in) standard, 368 mm (14.5 in) carbine, 508 mm (20 in) designated marksman, 254 mm (10 in) pistol‑length

508 mm (20.0 in)

3.2 kg (7.1 lb) empty (16 in barrel, without optics)

4.3 kg (9.5 lb) empty

30 rounds standard, 10/20/40/60 round options, drum magazines up to 100 rounds

20 rounds standard, 10‑round low‑profile magazines available for restricted markets

Direct‑impingement gas system (original) or short‑stroke gas piston (aftermarket/variant), rotating bolt, semi‑automatic or select‑fire

Roller‑delayed blowback, closed bolt

Single‑stage semi‑automatic trigger; military select‑fire models use a two‑stage fire selector with safe, semi, burst, and automatic modes

Single‑stage semi‑automatic trigger with manual safety lever

Standard: detachable flip‑up rear iron sight and fixed front post; many models equipped with Picatinny rail for optical, holographic, or night sights

Adjustable rotary drum rear sight (100‑800 m) and hooded front post; optional telescopic sight mounting rail on receiver cover