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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HK91, G3, HK33, HK53, HK93 Paddle Magazine Release - Anti-Rattle - USED
H&K Heckler & Koch
$42.95Heckler and Koch Anti Rattle Paddle Magazine Release for HK91, HK G3s and HK33, HK53, HK93 - USED This is a used German anti-rattle paddle mag release for installation on all Heckler and Koch Firearms .223 and .308 rifles. Compatible With: HK91,...HKP-22061$42.95 -
HK MR556 A4 Upper, Complete - Full Auto and Ejection Door
H&K Heckler & Koch
$845.95HK Heckler and Koch A4 Complete Upper with Full Auto Ejection Door for HK MR556 The HK 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...HKP-21929$845.95 -
On Sale
HK UMP Demilled Extended Rear Receiver Section
H&K Heckler & Koch
Now: $689.95Was: $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...HKP-19798Now: $689.95Was: $999.95 -
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 HK417HKP-16624$797.95 -
HK MR556, MR223 A5 Incomplete Upper Receiver
H&K Heckler & Koch
$489.95HK German Un-Assembled/Stripped HK MR556/MR223 A5 Upper Receiver Factory HK MR556 A5 upper receiver. This is the semi-auto MR556 variant. Compatible With: HK MR556 HK MR223 HK 416*** Need a matching lower for your build? STS416 A5 LOWER -...HKP-18785$489.95 -
On Sale
HK FMP G3 Early Type De-Milled Front End - No Cocking Handle Assembly
FMP HK CONTRACT
Now: $54.95Was: $68.95HK G3 - FMP Early Type De-milled Front End - No Cocking Handle Assembly Early style G3 front end with no hanger from de-milled FMP G3 parts kits. Perfect for custom builds. Includes: Cocking tube Trunnion Barrel pinHKP-22377Now: $54.95Was: $68.95 -
HK417, MR762 Charging Handle Plate
H&K Heckler & Koch
$19.95HK MR762, HK417 Plate For Charging Handle Compatible With: HK MR762 HK417HKP-16843$19.95 -
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...HKP-18629$1,285.95 -
HK21 Barrel Grip Axle Pin
H&K Heckler & Koch
$9.95HK21 Barrel Grip Axle Pin Factory axle pin for HK21 barrel handle release levers.HKP-15451$9.95 -
On Sale
HK MP5K, AP5-P Trunnion - 9mm
MKE
Now: $63.95Was: $79.95HK MP5K Trunnion Made to exact factory HK specifications for the HK MP5K type builds. Machined to HK spec making the install painless and hassle free. Compatible With: MP5K In spec clonesHKP-22522Now: $63.95Was: $79.95 -
HK MR556, MR223 Upper Receiver - BLEMISHED
H&K Heckler & Koch
$695.95HK MR556, MR223 Upper Receiver - BLEMISHED ONLY 1 UNIT AVAILABLE - AS PICTURED MISSING FORWARD ASSIST AND GAS PISTON COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE...HKP-16950-BL-B$695.95 -
On Sale
AR15 Buffer Tube - Hex - 7.5" - BLEMISHED
Sig Sauer
Now: $19.95Was: $44.95SIG Sauer Phase 5 Hex Buffer Tube for AR-15 Pistols - BLEMISHED ONLY 1 UNIT AVAILABLE - AS PICTURED COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE FINAL. This buffer...HKP-99304Now: $19.95Was: $44.95