Receivers / Flats / Uppers
Explore our premier selection of HK receivers, flats, and uppers at HKParts, perfect for building or upgrading your Heckler & Koch firearms. Our products feature precision-engineered MP5 receiver flats, HK 416 complete upper assemblies, and a wide range of custom options designed for tactical and precision shooting. Whether you are customizing an MP5, upgrading an HK416, or constructing a new firearm, our high-quality components provide unparalleled reliability and performance.
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MM HK PSG1/21E/23E Forward Complete Assist Assembly
Michaels Machines
$779.95MM HK PSG1/21E/23E Forward Complete Assist Assembly Michael's Machines US-made complete forward assembly or your HK PSG1, MSG90, HK21E/23E. A great option for a build now that the factory units are no longer available. Available exclusively...$779.95 -
HK417, MR762 Upper Receiver - Incomplete
H&K Heckler & Koch
$797.95H&K HK MR762/417 Upper Receiver - Incomplete Stripped upper receiver with threaded piston guide bushing installed. Compatible With: HK MR762 HK417$797.95 -
Out Of Stock
HK416, MR556 Upper 8" 416C Style Conversion Kit
HKP HK Parts
$1,285.95Upper Conversion Kit for HK416 and MR556 8 inch barrel - HK 416C Style Finally an answer for all of those that have been wanting as close to the original, rare unicorn of a find HK 416C 8" barrel conversion kit for 416 or MR556. Each conversion kit...$1,285.95 -
HK MR556 A4 Complete Upper - F/A & Ejection Door
H&K Heckler & Koch
$845.95H&K HK MR556 A4 Complete Upper w F/A Ejection Door The H&K MR556 A4 Complete Upper is a superior factory assembly that comes fully equipped with a forward assist and an ejection port door, providing unparalleled reliability and precision. This...$845.95 -
HK UMP Demilled Extended Rear Receiver Section
H&K Heckler & Koch
$999.95HK German Factory UMP Receiver Section - Extended Demilled factory HK UMP rear receiver section perfect for a USC-UMP conversion. With the folding stock attachment point intact right in front of the ejection port, this extended receiver section is...$999.95 -
Out Of Stock
HK416, MR556 Upper 9" 416C Style Conversion Kit
HKP HK Parts
$899.95MR556 & HK416 Upper Conversion Kit - 9" - HK 416C Style Finally an answer for all of those that have been wanting as close to the original, rare unicorn of a find HK 416C 9" barrel conversion kit for 416 or MR556. Each conversion kit upper or barrel...$899.95