Using the M249 in grazing fire effectively involves maintaining a low trajectory to ensure that rounds travel parallel to the ground, maximizing their effectiveness against enemy personnel. Position the weapon in a stable firing position with a clear line of sight to the target area while ensuring that the muzzle is elevated slightly to account for bullet drop at longer distances. Engage targets at close to medium ranges, ideally within 600 meters, and use continuous fire to suppress enemy movement and provide cover for advancing troops. Additionally, coordinating with team members for cover and situational awareness enhances the overall effectiveness of grazing fire.
The maximum effective range of the M249 light machine gun is 1,000 yards (910 meters).
700-1200 rpm.
In short the M249 is effective up to 1000 meters to cover an area target which the gun is designed to do.
The maximum effective range of a point target on the M249 is 800 meters. The maximum effective range of an area target is 1000 meters. The maximum range is about 3600 meters.
600 meters for a point target. 800 meters for an area target.
The M249 is an automatic light machine gun. This gun uses 5.56 mm ammunition. It is gas operated and air cooled. It has a quick change barrel. It can support a bi-pod attachment, allowing a boost in the already accurate rate of fire the gun possess.
The M249 Squad Automatic Weapon fires the same 5.56x45mm cartridge used by the M16 and M4.
CLP
FN Herstal
Technically the PKM, since it is an AK-47 variant it fires a 7.62mm round while the M249 shoots a smaller 5.56mm round
The basic load for a M249 light machine gun is typically 200 rounds of 5.56x45mm NATO ammunition. This is usually carried in the form of linked belts or disintegrating link belts, allowing for sustained fire in combat situations. Soldiers may carry additional ammunition in pouches or packs, but the standard load is designed for immediate engagement.
In the US military, you'd probably be referring to a squad's Automatic Rifleman, who carries the M249 SAW. Each fire team in an infantry squad has one, and their role is suppressive and supporting fire, particularly to lay down covering fire while the other fire team bounds, flanks around, or moves otherwise.