AR-15 variants Numbered Colt military models Numbered Colt military models

| Colt_model_no_ | Name_ | Stock | Fire_control | Rear_sight | Forward_assist | Case_deflector | Barrel_length | Barrel_profile | Barrel_twist | Hand_guards | Bayonet_Lug | Muzzle_device |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 905 | M16A4 | A2 | S-1-3 | Flattop | Yes | Yes | 20 in. | A2 | 1:7 | Ribbed | Yes | A2 |
| 920 | M4 Carbine | 3rd and 4th Generation | S-1-3 | Flattop | Yes | Yes | 14.5 in. | M4 | 1:7 | M4 | Yes | A2 |
| 921 | M4E1/A1 Carbine | 4th Generation | S-1-F | Flattop | Yes | Yes | 14.5 in. | M4 | 1:7 | M4 | Yes | A2 |
| 921HB | M4A1 Carbine | 4th Generation | S-1-F | Flattop | Yes | Yes | 14.5 in. | M4 HBAR | 1:7 | M4 | Yes | A2 |
| 925 | M4E2 Carbine | 3rd or 4th Generation | S-1-3 | Flattop | Yes | Yes | 14.5 in. | M4 | 1:7 | M4 | Yes | A2 |
| 927 | M4 Carbine | 4th Generation | S-1-F | Flattop | Yes | Yes | 14.5 in. | M4 | 1:7 | M4 | Yes | A2 |