SPW / Mk 46 Mod 0 / Mk 46 Mod 1

The Mk 46 is a gas-operated, air-cooled, belt-fed lightweight machine gun (LWMG) in use with United States special operations forces (SOF) since 2003. It is a variant of the M249 SAW light machine gun that has been designed by Fabrique Nationale (FN) to be as light and compact as possible and was tailored specifically for use by SOF.

The Mk 46 is a development of the M249 Special Purpose Weapon (SPW), which was the initial attempt to create SOF-specific SAW. The SPW design did away with the SAW's carrying handle, tripod-mounting lug and a magazine well for accepting M16-style magazines. The SPW added a 3-sided set of MIL STD 1913 Pictatinny rails around the forearm and 1 atop the receiver. The SPW features a collapsible buttstock of the sort found on the M249 PARA. The SPW's barrel is longer than the M249 Para but shorter than the full-length SAW. Like the M249, the SPW features a fold-down bipod. In the SPW's case, this bipod can be detached in order to save even more weight.

A M249 Special Purpose Weapon (SPW). Note the lack of bipod, carrying handle and mounting lug. The SPW and Mk 46 are designed for airborne special operations forces and so are as light and short as possible. The SPW is fed from a disintegrating belt of 5.56x45mm NATO ammo, in this case in a soft pouch attached to the weapon.

Mk 46 Mod O

The Mk 46 Mod 0 is almost identical to the SPW. This is the version of the LWMG that was adopted in large numbers by United States Special Operations Command (USSOCOM). Differences between the Mk 46 and SPW include a 4-sided rail system around the Mk 46's forearm and the SPW's callapsible buttstock is replaced with a the fixed polymer one found on the standard SAW.

A Mk 46 Mod 0. Note the fixed buttstock and 4-sided rail system on the heat shield.

A Ranger with the 75th Ranger Regiment armed with a Mk 46 fitted with an Aimpoint red dot sight.

photo : US DoD

Mk 46 Mod 1

The next iteration of of the Mk 46, the Mod 1, features an improved bipod assembly, reintroduction of the carry handle and reversion to standard M249-style heat shield thereby replacing the Mod 0's 4-sided rail interface with a 3-sided one.

Mk 46 Specifications

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