FN FNC vs M4A1

1983–Present

1994–Present

~250,000 estimated

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

910 mm (35.8 in) with stock extended, 730 mm (28.7 in) with stock folded

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

415 mm (16.3 in) standard, 305 mm (12.0 in) carbine version

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

3.45 kg (7.6 lb) empty, 3.80 kg (8.4 lb) with full magazine

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 available

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 (Safe/Semi/Auto)

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

Adjustable rear aperture (100–400 m) and hooded front post; optional rail‑mounted 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