M4 Parts Identification

This is the BMTSG's M4 parts-identification practice diagram — an unlabeled exploded view with numbered callouts (1–15) and no part names. Treat it as a self-test: name each numbered part of the M4 from memory, then check yourself against the labeled answers.

The parts you should be able to identify fall roughly into:

• Upper receiver — barrel, handguard, charging handle, forward assist, ejection port cover.
• Lower receiver — magazine well, trigger group, pistol grip, buttstock.
• Bolt carrier group (BCG) — bolt, bolt carrier, firing pin, cam pin, gas key.
• Sights — front sight post, rear sight aperture, optic (when issued).
• Sling and accessories.

For the labeled answers, see Module 4.1 — Weapons Familiarization, which has fully labeled diagrams of the upper receiver, lower receiver, and bolt carrier group.