FN F2000 vs M4A1

2001–Present

1994–Present

~150,000 estimated

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

790 mm (31.1 in) with stock folded, 860 mm (33.9 in) extended

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

508 mm (20 in) standard, 406 mm (16 in) for compact variants

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

2.95 kg (6.5 lb) empty, 3.45 kg (7.6 lb) loaded

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

30 rounds standard STANAG, 20‑round and 40‑round drum options

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

Short‑stroke gas piston, rotating bolt, closed bolt

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

Two‑stage military trigger with fire‑selector lever

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

Integrated 1.5× optical sight (foldable), backup iron sights, optional Picatinny rail for reflex or night sights

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