The Adaptive Combat Rifle, more commonly known as the ACR, is the production name for the Magpul Masada assault rifle. It is a potential replacement for the M4 carbine once formal requirements specifying requirements for the replacement of the M4 are written.
Developed over a period of five months, the ACR was originally intended to be a replacement to the M16 rifle. With an initial MSRP of $1500, the ACR was first shown off at the 2007 SHOT Show, and was originally slated to enter the market in 2008, but was pushed back to 2009 as the weapon's manufacturer, Bushmaster Firearms International, was currently focused on military products. With the help of renowned firearms designer Remington Arms, various design modifications to the ACR were made to allow it to endure harsh conditions. As of 2010, the ACR has entered the market, with Remington marketing select-fire variants of the rifle to the US military and law enforcement agencies and Bushmaster marketing semi-automatic variants of the rifle to civilians. The current MSRP of the ACR ranges from $2681 – $3061, which has caused much outcry due to the current suggested price being close to or more than twice as much as the original ACR's MSRP.
Unfortunately, Bushmaster had to issue a recall of all ACRs in 2010. Instructions were given to all ACR users to immediately discontinue use of their rifle, along with instructions on who to contact for an RMA. The reason for the recall, as stated by Bushmaster, was due to a potential performance issue with some ACRs which could accidentally slam fire.
The ACR was one of the contenders in the now-cancelled Individual Carbine competition, where the initial design was originally submitted; an improved design was later unveiled by Remington in 2011, specifically for the competition. The improved ACR had various new improvements such as a folding charging handle, a strengthened magnesium lower receiver and an M16A2-styled pistol grip among other refinements, with these refinements making the weapon 1.8 pounds (0.82 kilograms) lighter.
Two variants of the ACR were later spawned from this, including the ACR-C, a shortened version of the ACR with a folding stock and shorter barrel when compared to the full-size ACR, and even a designated marksman rifle variant.
A combination of several different rifle designs, the ACR is heavily based on the Magpul Masada, and combines design elements from firearms like the AR-15's action, the FN SCAR's charging handle location and the Heckler & Koch G36's liberal use of polymer components and parts into one single firearm design. The weapon's controls are completely ambidextrous and like most modern rifles, is of a modular design, which allows the ACR to be configured for a variety of different roles, all within a matter of minutes.
The military ACR has a three-position selector switch, with safe, semi-automatic and fully automatic settings. The charging handle is usually seen on the left of the rifle, although it can be pulled out and installed on the right of the rifle, making it friendly to left-handers. While the ejection port is located on the right hand side of the weapon, as is the case with most rifles, the ACR comes equipped with a case deflector, which deflects the cases away from the shooter's face, which makes it even more friendly to left-handers. Simply by changing some components of the ACR, the military ACR can be caliber-swapped from 5.56×45mm NATO to 6.8mm Remington SPC, although variants chambered in 6.8mm Remington SPC to begin with are currently in development. The military ACR's handguard is made of aluminum and can be fitted with various amounts of Picatinny rails.
The civilian ACR is also of a modular design, and uses many AR-15 compatible parts. The bolt group has been somewhat simplified and has been made into a single unit, with the addition of a captive return spring. The bolt is of a rotating multi-lug design which locks into the breech face. The civilian ACR can also be caliber-swapped from 5.56×45mm NATO to 6.8mm Remington SPC, just like its military counterpart, although variants chambered in 6.8mm Remington SPC to begin with are also currently in development. The civilian ACR's handguard is made of polymer and has heat shields and an aluminum tri-rail.
Both variants of the ACR take 30-round Magpul PMAGs, a high-strength polymer magazine designed for AR-15-patterned rifles and the Magpul PDR. As the PMAGs are STANAG compliant, the ACR can also use standard STANAG magazines. Both the civilian and military versions have ambidextrous magazine releases, and users are able to swap out the factory-installed stock and change them out for other Magpul stocks on both versions, along with the ability to swap out pistol grips and other components, making the ACR an extremely modular weapon.