M16 vs M4A1

1964–Present

1994–Present

8,000,000+ units (including all variants and licensed production)

~10,000,000+ units (including all variants and licensed production)

990 mm (39 in) with stock extended; 860 mm (33.9 in) with stock collapsed (carbine)

838 mm (33.0 in) stock extended, 756 mm (29.8 in) stock collapsed

508 mm (20 in) standard; 406 mm (16 in) for carbine variants

368 mm (14.5 in) standard; 406 mm (16 in) for the M4A1 SOPMOD variant

3.26 kg (7.2 lb) empty, standard rifle; 3.40 kg (7.5 lb) carbine

3.07 kg (6.8 lb) empty, 3.74 kg (8.2 lb) with full 30‑round magazine

30 rounds standard STANAG; 20, 40, 60 round options and drum magazines available

30 rounds standard STANAG, 20‑round low‑profile, 40‑round drum, 60‑round Beta‑C‑Mag available

Direct‑impingement gas system with rotating bolt, short‑stroke operation

Short‑stroke gas piston (M4A1 variant) with rotating bolt; original M4 uses direct‑impingement

Single‑stage military trigger; three‑round burst mechanism on A2/A4 models

Two‑stage military trigger, full‑auto only selector on M4A1; semi‑auto on standard M4

Standard: detachable carrying handle with integrated rear aperture (M16A1) or flat‑top receiver with Picatinny rail and removable iron sights (A4); front post fixed

Standard: A2 front post and rear flip‑up aperture; optional: MIL‑STD-1913 Picatinny rail for aftermarket optics, tritium night sights, or holographic sights