HK MR556 Upper Receiver Kit w/ Buffer and Spring

Regular Price: $2,069.00
Our Price: $1,899.00
MPN: 235975-A5
UPC: 642230247505
Out of stock
as of 06/13/2021 3:30AM CST

Store Inventory
Available OnlineOut of stock
Fountain Valley, CAOut of stock
The Colony, TXOut of stock
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Inter-Store Transfer

If this item is out of stock at your local RifleGear but available at our other location, no problem. Just place your order and select In-Store Pickup as the shipping method. As long as the item is legal in your location, we will transfer the item for you. You will be notified by e-mail when your item arrives.

The MR556A1 Upper Receiver Kit includes a complete upper receiver/barrel assembly, bolt carrier assembly, buffer, and buffer spring allowing most high-quality 5.56 mm AR-style rifles to be retrofitted to HK’s pusher rod system. The Upper Receiver Kit is the core of the HK 5.56 mm proprietary gas piston operating system. It employs a piston and a solid operating “pusher” rod in place of the gas tube normally found in AR15/M16/M4-style firearms Due to the shortened length of the HK buffer and HK  (action) buffer spring, these parts do not work in fixed stock AR-type rifles. 

Installation of MIL-SPEC hammers in non-HK lower receivers is required for reliable function. Notched hammers and reduced weight hammer springs are not compatible with this upper.

Additionally, the MR556A1 Upper Receiver Kit does not work in lower receivers with fully automatic or selective fire mechanisms.

HK 16.5 inch cold-hammer forged barrel
Upper receiver with forward assist, extended convertible charging handle,
HK Free Floating Rail System handguard
Complete MR556 Bolt Group Assembly
Tungsten Filled HK Proprietary Buffer
HK Proprietary Buffer (Action) Spring

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