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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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 HK23EHKP-21907$14.95 -
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...HKP-21828$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.HKP-16481$79.95 -
HK417, MR762 Upper Receiver and Handguard - Flecktarn
H&K Heckler & Koch
$1,489.95HK417, MR762 Upper Receiver and 13.5" Handguard - Flecktarn Factory HK MR762 matching flecktarn upper receiver and 13.5" handguard. ONLY 3 SETS AVAILABLE AND WILL NOT BE RESTOCKED Compatible With: HK MR762 HK417HKP-99325$1,489.95 -
On Sale
HK MP5 Trunnion - .40 S&W, 10mm - Factory - USED
H&K Heckler & Koch
Now: $297.95Was: $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.HKP-99173Now: $297.95Was: $549.95 -
Out Of Stock
HK UMP Paddle Magazine Release Assembly, Complete
USA
$19.95UMP Paddle Magazine Release - US Made - Assembly Complete New UMP Mag release. This is a very common repair and replacement part as they are fairly easy to break on the UMP lower. Simple and easy to install no gunsmith needed or required. Compatible...HKP-19499$19.95 -
Out Of Stock
HK416, MR556 Upper Conversion Kit - Threaded 1/2x28, - 5.56x45 / .223
HKP HK Parts
$699.95H&K MR556 & HK416 (5.56x45/.223) Upper Conversion Kit - Threaded 1/2x28 Finally an answer for all of those that have been wanting a 14.5" upper for an HK416 or MR556. This conversion kit adds an upper or a barrel option for your MR556, CR556...HKP-17877$699.95 -
Out Of Stock
HK USC Magazine Release - Extended
HKP HK Parts
$24.95HKP HK Parts Alloy Extended Magazine Release for HK USC Billeted alloy USC magazine release. This is a very common repair and replacement part as they are fairly easy to break on the USC lower. With this new metal mag release you get more surface area...HKP-17918$24.95 -
Out Of Stock
HK UMP Rear Receiver Section - Demilled
H&K Heckler & Koch
$0.00HK UMP Demilled Receiver Section This is a demilled factory HK UMP rear receiver section that is perfect for the new Tom Bostic USC-UMP conversions. This section is the perfect length in order to do the USC, UMP conversion. Last one available.HKP-01659$0.00 -
Out Of Stock
HK UMP Paddle Magazine Release
USA
$9.95US Made Paddle Magazine Release for HK UMP New UMP Mag release. This is a very common repair and replacement part as they are fairly easy to break on the UMP lower. Simple and easy to install no gunsmith needed or required. Compatible With: UMP Please...HKP-18773$9.95 -
Out Of Stock
HK21 Trunnion
H&K Heckler & Koch
$0.00US Made HK21 Trunnion By Michael's Machine (MM) These are the finest US-made trunnions available.HKP-00246$0.00 -
Out Of Stock
HK23E Feed Mechanism - Complete - 5.56 / .223
Michaels Machines
$3,999.95MM HK 23E (5.56/.223) Complete Feed Mechanism New US manufactured HK23E feed mechanism complete with top plate and push pin. The complete unit a great spare to have on hand. Compatible With: Factory HK23E and MM23E firearmsHKP-17578$3,999.95