HK MR556A1 Upper Receiver Kit


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HK MR556A1 Upper Receiver Kit


HK MR556A1 Upper For Sale

HK MR556A1 Upper For Sale Online

The Heckler & Koch MR556A1 Upper Receiver Kit is the core of the HK 5.56mm proprietary gas piston operating system. This complete kit includes the upper receiver/barrel assembly, a bolt carrier assembly, buffer and the buffer spring that allows high quality 5.56mm AR style rifles to be retrofitted to HK’s pusher rod system. HK’s MR556 Upper offers a solid operating ‘pusher’ rod in place of the gas tube that is normally found in AR15/M16/M4 style firearms.

HK has designed the MR556A1 Upper Receiver Kit to be fully interchangeable with all high end AR style weapons. It is easily attached to an AR lower receiver with standard takedown pins. An HK piston driven operating system eliminates malfunctions common to direct impingement gas systems. Hot carbon fouling and waste gases never enter the receiver area. Military and Law Enforcement users have enjoyed this feature on the HK416 upper receivers. Engineered for a variety of quality 5.56 X 45mm ammunition, the MR556 Upper is also compatible with most quality .223 Remington ammunition.

Features of the MR556A1 Upper Receiver include a 16.5 inch barrel with an internal profile of 6 lands and grooves with a 1:7 twist. A slightly smaller, internal diameter, at the muzzle end creates a positive effect on bullet accuracy and velocity. Accuracy is also increased with the thick, heavy contour. Addition features include the HK Free Floating Rail System (FFRS) handguard with four MIL-STD-1913 Picatinny rails. It can also be fitted with accessories, sights, lights and aimers that are compatible with M4/M16 type firearms.

The HK MR556 Upper Receiver Kit Includes:

  • Complete MR556 Upper Receiver/Barrel Assembly
  • Barrel: 16.5 inch, cold-hammer forged
  • Forward Assist
  • Extended Convertible Charging Handle
  • MLOK Handguard
  • Complete MR556 Bold Group Assembly
  • Buffer: Tungsten Filled HK Proprietary
  • Buffer Spring: HK Proprietary

Xtreme Guns and Ammo is one of the nation’s top Heckler and Koch Firearms Dealers. XGA carries a huge inventory of HK Pistols, HK Rifles and HK Magazines and Accessories in Stock and on Sale. Feel free to call 832-363-3783, or chat with us online, for answers to all of your HK questions and needs.

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