M433 vs M4A1

2017–present

1994–Present

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

33.8 in (860 mm) with 16.5 in barrel

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

11–20 inches (varies)

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

3.5 kg (7.7 lb)

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

30-round STANAG

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

Gas-operated, short-stroke piston

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

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

Iron sights or optics

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