[5] It is constructed with modularity for the United States Special Operations Command (SOCOM) to satisfy the requirements of the SCAR competition.

Both types are available in Close Quarters Combat (CQC), Standard (STD), and Long Barrel (LB) variants.

In early 2004, United States Special Operations Command (USSOCOM) issued a solicitation for a family of Special Operations Forces Combat Assault Rifles, the so-called SCAR, designed around two different calibers but featuring high commonality of parts and identical ergonomics.

[2] The U.S. Special Operations Command later cancelled their purchase of the SCAR-L and planned to remove the rifle from their inventory by 2013.

The rifle uses a "tappet" type of closed gas system much like the M1 carbine while the bolt carrier otherwise resembles the Stoner 63 or Heckler & Koch G36.

The SCAR is built at the FN Manufacturing, LLC plant in Columbia, South Carolina, in the United States.

Since 2008, FN Herstal has been offering semi-automatic versions of the SCAR rifles for commercial and law enforcement use.

In July 2007, the United States Army announced a limited competition between the M4 carbine, FN SCAR, HK416, and the previously shelved HK XM8.

Since a percentage of each weapons' stoppages were caused by magazine failures, the FN SCAR, XM8 and HK416 performed statistically similarly.

This test was based on two previous systems assessments that were conducted using the M4 carbine and M16 rifle at Aberdeen Proving Ground in 2006 and the summer of 2007 before the third limited competition in the fall of 2007.

The weapon is similar to the SCAR Mk 16 Mod 0 but with modifications including a 140 g (0.3 lb) weight reduction resulting in a loaded weight of 3.61 kg (7.95 lb), a bayonet lug for an M9 bayonet (which the Mk 16 does not have), a rail mounted folding front iron sight instead of the gas block mounted sight, and a non-reciprocating charging handle.

[citation needed] In late October 2010, SOCOM approved full-rate production of the Mk 20 sniper variant of the SCAR, with fielding beginning in mid-May 2011.

[10] On 25 June 2010, SOCOM announced that it was cancelling the acquisition of the Mk 16, citing limited funds and a lack of enough of a performance difference in comparison to other 5.56mm rifles to justify the purchase.

[39] FN Herstal though had refuted that the Mk 16 was being dropped from the inventory and stated that the 5.56mm variant will be retained by SOCOM, and that "The choice between the 5.56 mm and the 7.62mm caliber will be left to the discretion of each constitutive component of USSOCOM's Joint Command (e.g.

SEALs, Rangers, Army Special Forces, MARSOC, AFSOC) depending on their specific missions on today's battlefield".

To maintain the SCAR as a small-caliber weapon, they are procuring conversion kits for the Mk 17 battle rifle to make it fire 5.56×45mm rounds.

[42] The presolicitation for the SCAR program originally called for one rifle that could be adapted to fire multiple calibers including 5.56mm, 7.62×51mm, and 7.62×39mm.

[44][45] Navy special operations forces procures their firearms through SOCOM and fielded the MK 16 more than any other unit.

[37] The Mk 17 was in widespread use by American SOF units in Afghanistan, where its relative light weight, accuracy and stopping power has proved of worth on the battlefield.