Whatever you want to use. If you have an RAS on it, you could put a foregrip, tactical light, PAC-4/PEQ-2/any other infrared aiming device, optics (EOTech, AimPoint.. some customers might use the MEPRO21), could could attach a grenade launcher or something like a KAC Masterkey breaching shotgun to it. Normal line units would typically have some sort of optic (EOTech, AimPoint, or Trijicon ACOG), rear backup iron sight, PAQ-4 or PEQ-2 infrared laser, and some sort of visible light. A rear area unit, however, isn't likely to use any of these, and may not even have the RAS, instead using just the standard heat shields and iron sights.
The M4 CARBINE IS BETTER THAN THE M16.
No one will give you an M4 rifle/carbine for free.
M4 is the carbine- shorter barrel
The M4 is a military rifle capable of semi automatic or 3 shot automatic fire. It is used where a lighter shorter rifle is useful.
The Colt M4 Carbine .22 is a replica of the real M4 but in .22 caliber.
There is an M4 carbine in Call of Duty: Modern Warfare 2.
Another name for M4 is the "M4 Carbine." It is a lightweight, air-cooled, gas-operated, magazine-fed carbine that is widely used by the U.S. military and other armed forces around the world. The M4 is known for its versatility and adaptability, often featuring a collapsible stock and a Picatinny rail for mounting accessories.
The U.S. military primarily uses the M4 Carbine, which is manufactured by Colt's Manufacturing Company under the designation M4. The M4 is a gas-operated, air-cooled, magazine-fed carbine that is widely used by various branches of the military. Other manufacturers, such as FN Herstal and Remington, have also produced M4 variants under military contracts.
The M4 carbine has a muzzle velocity of 2,970fps(884m/s).
5.56mm
The weapons were a k47s and rpgs. most common the rpd or m4 carbine.
While the M4 Carbine is intended to fire a 5.56x45mm NATO round that is distinct from the .223 Remington, both are centerfire cartridges. So yes, the M4 Carbine is a centerfire rifle.