Heckler & Koch HK MR556A4 11″ 5.56 MLOK Upper Receiver Group
Now available separately as a standalone upper group that drops right onto your existing AR lower, providing the quality and legendary performance that Heckler & Koch is known for.
The latest update from HK-USA to the commercial variant of the legendary HK416, the MR556 A4 and MR762 A4 represent an enhanced example of “no compromise” HK performance.
Its short-stroke gas piston operating system does not impart hot carbon fouling back into the action, allowing the weapon to run longer, with less maintenance and with less wear on internal components than direct-impingement ARs. Its adjustable gas regulator allows the operator to tune the action specifically for suppressed or unsuppressed operation. Fully ambidextrous controls, lighter weight and a slimmer profile make the new A4 easier to operate, manipulate and employ.
For those who demand an AR with unmatched capability and uncompromising reliability and durability, the MR A4s remain the top tier solution.
Complete upper receiver group with barreled upper, bolt carrier group, charging handle, HK heavy buffer and buffer spring. Compatible with only carbine receiver extensions and not A5 or rifle extensions.
Compatibility Note: These uppers utilize a firing pin safety in the bolt carrier group to prevent the possibility of a slamfire. These uppers will not work with certain types of triggers. Please visit this HKPRO thread to check trigger compatibility, here.
Specifications
- Caliber: 5.56mm
- Color: Black
- Upper Receiver: Forged, HK MR556A4
- Bolt Carrier Group: 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
jafulton13 (verified owner) –
thanks for another good experience sol, really need to just try and buy stuff from you guys exclusively. Not just HK stuff but gucci stuff in general. This upper arrived at my house in like 48 hours, impressive from Arkansas. Communication is on point af, especially for exclusively email comms.
For HK USA’s first yeet into the space, a shorter 5.56 caliber upper that’s piston driven and gas adjustable stock is neat. I am an HK nerd so I’m biased though. When my 16.5 arrives and I can shoot the complete system, I’ll leave another review. One things for sure though- will come here for my T-2 and unity mount for this upper! Thanks sol!
Alan B (verified owner) –
Awesome upper. Super fast shipping. My go to dealer for H&K stuff from here out.
jonpro88 (verified owner) –
Thanks for getting it to me fast, Sol. So far this upper has been excellent. It’s softer shooting than my KAC CQB, even softer when suppressed. If the HK proves to be as reliable, the KAC may be taking a back seat.
Cory S (verified owner) –
This upper is fantastic. Ejection is consistent and it shoots very smooth for a piston system. Haven’t had any issues so far with around 500 rounds with and without my can. Rooftop defense has solid customer service and fast shipping. Would highly recommend both them and this upper.
Pat Murray (verified owner) –
Rooftop Defense is top notch ! Great comms. Fast shipment and competitive prices