The M249 SAW (Squad Automatic Weapon) is the light support weapon currently used by the U.S. Army today on the squad level. The M249 fires the same 5.56 x 45mm ammunition as the M16, and can even use the M16 magazines. However, the M249 is more commonly fed from a 200 round box magazine. The weapon only has safe and fully automatic modes of fire.
The SAW is a belt fed automatic weapon using 100-round box magazines used by support soldiers. It's high rate and of fire allows the Support Gunner to lay down suppressive fire as well as cover fire for his squad. It was developed by the Belgian company FN Herstal in the late 1970's early 1980's.The folding bipod is mounded under the gas chamber, and the gun has provisions for tripod or vehicle mountings. The open sights are standard, with the availability of wide variety of optical and night sights for SPW and Mk.46 versions with Picatinny rails.
The MK.46 is a designation given to M249's that has been issued to Special Forces, by US SOCOM. The only difference between this and the standard version, is that the MK.46 has no magazine feed module. It can only be fed by a specially designed plastic box, holding a 200-Round belt or a smaller, lighter 100-Round soft bag pouch and is clipped beneath the receiver.