Two variants of the M4 are featured in Battlefield 3.
— Battlelog description
The M4A1 is a weapon featured in Battlefield 3. It was first seen in the Fault Line Trailer.
The M4A1 is Blackburn's primary weapon in Operation Swordbreaker and in the second half of Operation Guillotine. It is also Miller's primary weapon in Thunder Run when on foot. Campo uses the M4A1 throughout the campaign. Cole is always equipped with the M4A1. Blackburn, Campo, and Miller have used the M4A1 with a Holographic Sight. Blackburn and Cole have used the M4A1 with an ACOG sight.
The M4A1 is the default carbine for the United States Marine Corps Engineer kit. It is capable of fully-automatic or semi-automatic fire, has low recoil, making it very accurate at medium and short ranges. It can do a fairly high amount of damage due to its fast firing speed.
The weapon's main strength is its versatility which is due to a combination of its rate of fire, which is one of the fastest of all Carbines, its easily controllable recoil, and extremely fast reload time, the fastest out of the Carbines. However, the M4A1, along with the M4, has the second-highest first shot recoil multiplier at 2.8x, after the A-91, which is helped by using Flash Suppressor. Although it does not reduce first shot recoil, it does reduce horizontal recoil, making sustained tapfiring somewhat easier at medium ranges.
The M4A1 and AKS-74u are the last Engineer unlocks for 145,000 points which allows the player to have the weapon from the other faction, allowing USMC Engineers to use the AKS-74u and Russian Ground Forces Engineers to use the M4A1.
— Battlelog description.
The M4 is a weapon featured in Battlefield 3 and is unlocked upon obtaining a 40,000 Engineer score. It has the same stats as the M4A1, but fires in either three-rounds burst or semi-automatic. After a recent patch, the M4 has the same vertical recoil and less horizontal recoil than the M4A1. The M4 can be used by both factions and share its unlocks with the M4A1.One thing to notice, is that the M4 has a much tighter bullet spread than its automatic counterpart. While not significantly important within burst fire ranges, it can be useful on larger maps where semi automatic fire can be required. In addition, when a heavy barrel is added, the M4 is the most accurate carbine, beating both the SCAR-H and ACW-R. The M4, along with the M4A1, has the second-highest first shot recoil multiplier at 2.8x, after the A-91, which is helped by using Flash Suppressor. Although it does not reduce first shot recoil, it does reduce horizontal recoil, making sustained tapfiring somewhat easier at medium ranges.
- In the Pre-Alpha stages of Battlefield 3, as seen in the Fault Line trailers, the M4A1's appearance was that of Medal of Honor's M4A1 multiplayer model, which DICE helped develop.
- In the Pre-Alpha the player pulled the charging handle of the M4A1 rather than hitting the bolt release in the Retail.
- The M4A1 has Magpul Ranger Plates on the bottom of its STANAG Magazine.
- The M4A1 reload animation has slightly changed in full release.
- There was a glitch that, once the M4A1 Russian Acquired version was unlocked, the AKS-74u and M4A1 would stay faction specific and the player would have to keep switching back and forth if they wanted to keep using one or the other. DICE has fixed this bug in the 1.04 patch.
- While using the M4A1 as a Russian, the meter below the ammo counter doesn't show how far you are from unlocking another attachment. This applies to all faction-specific weapons acquired by the other faction.
- The M4A1 is actually painted with a tan camouflage in the game. It is noticeable in bright environments, but when there is shade, it looks like the blackish-grey color seen in almost every other picture of it.
- The M4A1 in Battlefield 3 has a Snake design on the magazine well as in the Medal of Honor version, of which DICE helped develop the game's multiplayer.
- The proficiency dog tag shows the M4A1 with an ACOG and Foregrip equipped.