Search
Cart
There are no items in your cart.
Login
HK MR556 A4 11" Upper Receiver Kit
Item #: 51000385 | Be the first to review this productThis kit includes a complete upper receiver/barrel assembly, allowing Mil-Spec 5.56mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system. This system utilizes a piston and a pusher rod in place of the gas tube normally found in AR15/M16/M4-style rifles. This closed system virtually eliminates the malfunctions that are common in direct-impingement gas systems, since hot carbon fouling and waste gasses are not propelled into the receiver area to operate the action. This is the same key feature critical to the success of the HK416 used by elite military and law enforcement customers. Upper will ship in HK Soft case.
The MR556 A4 Upper kit includes
1. Complete MR556 upper receiver/barrel assembly, barrel, upper receiver with forward assist, extended
charging handle and free-floating slimline handguard.
2. Complete MR556 bolt group assembly
3. HK proprietary buffer and action spring
All sale are final, this Upper kit is non returnable .
Click below to be notified when this item is back in stock.
You must be logged into your account to receive notifications.
Specifications
- Caliber: 5.56mm
- Color: Black
- Upper Receiver: Forged, HK MR556A4
- Bolt Carrier G: MR556A4
- Rail: MLOK
- Barrel: 11″ Cold Hammer-Forged Barrel, 1:7 Twist
- Gas System: Short-Stroke Gas Piston
- Gas Block: Adjustable
- Charging Handle: HK Ambidextrous
- Muzzle Device: Birdcage
- Buffer Assembly: HK Heavy Buffer
- Compatible with most AR-15 and M4 lower receivers.
- Needs a carbine-length buffer tube or a rifle buffer tube spacer (must be customer provided).
- Needs a “mil-spec” style hammer to disengage the firing pin safety
Technical Compatibility Notes:
NEWSLETTER
Blue Ridge Supplies is a preferred distributor of Heckler & Koch pistols, rifles and firearm accessories. We are dedicated to providing a fast, efficient and secure customer experience.
CONTACT US
-
Number: 610-730-6313
Mon-Fri 9am to 7pm EST -
blueridgesupplies@rcn.com
© Copyright 2025. Blue Ridge Supplies | HKPartsPro.com. All Rights Reserved.
