Description
This kit includes a complete upper receiver and barrel assembly, allowing Mil-Spec
5.56mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system.
This system uses 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 gases 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.
What you receive
- Complete HK MR556 upper receiver and barrel assembly, 5.56mm
- M-LOK handguard with full-length top rail
- Bolt carrier group
- Buffer and buffer spring
- Ships in an HK soft case
Specifications
- Caliber: 5.56 × 45 mm
- Barrel length: 11 in.
- Barrel profile: 6 lands & grooves, right twist, 1 in 7 in.
- Sight radius: 14.60 in.
- Sights: optics ready
- Overall length: 17 in.
- Width: 3.07 in. · Height: 2.68 in.
- Complete kit weight: 4.20 lb.
Fitment
Designed to drop onto Mil-Spec AR15, M16 and M4 pattern lower receivers. Confirm your
lower is Mil-Spec before ordering — the piston system relies on standard receiver
dimensions.
Shipping
Ships free. An upper receiver assembly is not a serialized firearm
under federal law, so in most places it ships directly to you rather than to a dealer and
no FFL transfer is required. Some states set their own rules — it is the
buyer’s responsibility to confirm the item is legal where they live before
ordering.
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