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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HK MR762 A4 Buffer Tube
H&K Heckler & Koch
$95.95H&K MR762 A4 Buffer Tube Factory German-made buffer tube for the MR762 A4. Compatible With: HK MR762 A1/A4$95.95 -
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 -
HK416, MR556 Complete Buffer Tube
H&K Heckler & Koch
$176.95H&K HK416, MR556 Complete Receiver Extension/Buffer Tube Genuine German complete receiver extension for the 416 based 5.56 / .223 platforms. Compatible With: HK416 MR556$176.95 -
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 -
On Sale
HK417, MR762 Extension Nut - Buffer Tube - Castle Receiver - BLEMISHED
H&K Heckler & Koch
Now: $18.71Was: $39.95H&K HK MR762/417 Castle Receiver Extension Nut For Buffer Tube - Black - BLEMISHED ONLY 2 UNITS AVAILABLE - AS PICTURED COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES...Now: $18.71Was: $39.95 -
HK MP5 Receiver Flat - 9mm - no Sling Clip
HKP HK Parts
$189.95HKP HK MP5 9mm Receiver Flat w/o Sling Clip The MP5 9mm receiver flat serves as the foundation for custom MP5 builds. This version does not include a sling clip cutout, offering flexibility for customization. Precision-engineered for compatibility with...$189.95 -
Out Of Stock
HK33, HK53, HK93 Rear Receiver Section
H&K Heckler & Koch
$79.95H&K 93/53/33 (5.56/.223) Rear Receiver Section Each rear receiver section is from a factory German HK 33/53 that was demilled and includes the welded on rear sight base and push pin bushing intact.$79.95 -
HK MR762 A4 Upper Receiver Kit - 16"
H&K Heckler & Koch
$2,449.95HK UPPER RECEIVER KIT MR762 A4 - 16" The MR762 A4 upper kit contains a complete upper receiver and barrel assembly. The closed system design significantly reduces malfunctions typically associated with direct-impingement gas systems, as hot carbon...$2,449.95 -
On Sale
AR15 Buffer Tube - Hex - 7.5" - BLEMISHED
Sig Sauer
Now: $14.96Was: $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...Now: $14.96Was: $44.95 -
On Sale
HK416, MR556 Receiver End Plate - AS IS - BLEMISHED
Now: $7.95Was: $19.95HK MR556/416 Receiver End Plate - BLEMISHED CONDITION MAY VARY - SEE PHOTOS INSTALLATION MARKS. COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE FINAL. Aftermarket...Now: $7.95Was: $19.95 -
On Sale
HK MP5 Trunnion 10mm / .40 S&W - Factory - USED
H&K Heckler & Koch
Now: $223.46Was: $549.95H&K MP5 40/10 Factory Trunnion - USED ONLY 1 UNIT AVAILABLE - AS PICTURED Used genuine German trunnion with round guides. Compatible With: HK MP5 40/10 THIS CLOSEOUT PART IS NOT ELIGIBLE FOR RETURN, REFUND, OR EXCHANGE. SALE IS FINAL.Now: $223.46Was: $549.95 -
HK21E, HK23E Left Receiver Reinforcement Rail Weldment
H&K Heckler & Koch
$14.95H&K 21E/23E Left Receiver Reinforcement Rail Weldment Genuine German-made weldment for left-side receiver reinforcement rail. Precision-machined using the correct steel and milling for you HK21E or HK23E build. Compatible With: HK21E HK23E$14.95