H&K 51000385 MR556 Upper Receiver Kit 5.56mm AR15/M16/M4 A4 Features
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HK MR556 Upper Receiver Kit 5.56mm - Model 51000385 - UPC: 642230270220
The HK MR556 Upper Receiver Kit is designed to retrofit Mil-Spec 5.56mm AR-style rifles with HK's advanced piston and pusher rod system. This system replaces the traditional gas tube, significantly reducing malfunctions by preventing hot carbon fouling and waste gases from entering the receiver. This technology is a key feature of the HK416, trusted by elite military and law enforcement units. The kit includes a complete upper receiver/barrel assembly and ships in an HK soft case.
Specs:
Technical Specifications
| Caliber | 223 REM | 5.56 NATO |
|---|---|
| Barrel Length | 11.00" |
| Action Type | Piston |
| Finish | Matte Black |
| Weight | 8.80 oz |
| Twist Rate | 1-in-7 |
| Manufacturer | Heckler & Koch |
| Model | 51000385 |
| SKU | L1210666 |
| UPC | 642230270220 |
| Availability | In Stock |
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Shipping & Returns
Shipping Information
- Orders typically process within 1-2 business days
- Ships via major carriers with tracking
- Tracking information provided for all orders
- Shipping costs calculated at checkout based on weight and destination
Return Policy
- 30-day return policy on accessories and non-firearms
- Items must be unused and in original packaging
- Contact us for return authorization before shipping items back
- Original shipping costs are non-refundable
Questions?
Contact us at 502-272-4859 or submit a question for assistance with shipping or returns.
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