The M4A1 (stylized as gun_m4a1) is an assault rifle test weapon. It has a high rate of fire and a reload mechanism. The M4A1 takes the standard number 2 assault rifle slot. It does not have visible bullets by default, though the bullet impacts can be observed. It is based off of the real-life M4A1 Carbine.
The M4A1 has an incredible fire rate and is the fastest weapon in the game. It also maintains a surprisingly good accuracy and can fire an almost straight stream of bullets. Its projectiles have the power of a standard rifle. This is one of the experimental weapons, like the Glock.
The M4A1's magazine contains 30 rounds, which can be unloaded in about two seconds. The weapon fires 15 shots per second, which is roughly the same as its real-life counterpart. Occasionally, the weapon will glitch and only fire a single shot before having to reload. If the player tries to fire in bursts or 'semi-automatic' the M4A1's capacity will likely be reduced to 16 rounds until the next reload.
- This gun is frowned upon by the developer and can't be found in approved maps. This may be because it is not a fair weapon to fight with, in terms of damage and fire rate.
- This gun has been around since the beginning of the game as a test weapon. However, the weapon first appeared in customs maps on June 9, 2012.
- It is excellent for flying.
- The Glock was found a day later after someone discovered the M4A1.
- When the player reloads the weapon, the magazine seems to disappear then reappear.
- The M4A1 can be modified using the gun modifications triggers. This allows map makers to give the gun visible bullets.
- Another way to make the bullets visible is use the debug cheat.
- Firing the M4A1 in 'semi-automatic' is difficult because its high rate of fire typically yields two or three shots per click.
- This Weapon was removed from the weapon list in the switch to the Advanced Editor and was only available via the Old Editor, until Version 1.25 added the Combat Rifle CS-OICW and subsequently re-added the M4A1 and its sister weapon the Glock back into the level editor.