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 MP5, MP5K Contact Piece for Paddle Mag Release
H&K Heckler & Koch
$59.95Heckler and Koch 9mm Contact Piece for Paddle Mag Release for HKMP5 and HK MP5K - German This is the real deal NOT the .308 or .223 contact piece. Hard to find factory-correct, brand-new, latest production German HK 9mm contact piece. Compatible...HKP-00118$59.95 -
Picatinny Rail for HK Receivers - 13 Slot
DTAC Dakota Tactical
$74.95DTAC Picatinny Rail For HK Receivers - 13 Slot Mil-Spec all steel picatinny rail in the white, relief cut for HK receivers & made for mounting scopes and optics to HK builds. This unit easily welds to the top of your HK receiver. Compatible With: HK...HKP-17818$74.95 -
HK UMP, USC Lower Locking Pin
H&K Heckler & Koch
$36.95HK German UMP Lower Locking Pin For use with all HK UMP lowers and USC to UMP conversions. New HK German manufacture.HKP-00595$36.95 -
HK91, G3 Magazine Catch
H&K Heckler & Koch
$19.95Heckler and Koch Magazine Catch for HK G3 and HK91 High-quality HK German production units are brand-new. These also have the proper newer style cut in them and round shafts. Compatible With: HK91, G3 PTR91HKP-02073$19.95 -
HK416, MR556, HK417, MR762 Bridge
H&K Heckler & Koch
$24.95Heckler and Koch HK416, HK MR556, HK417, and MR762 Bridge For Lowers Compatible With: HK416, MR556 HK417, MR762HKP-02676$24.95 -
HK UMP Magazine Release Axle
H&K Heckler & Koch
$19.95Heckler and Koch Magazine Release Axle for HK UMP Replacement magazine release axle for HK UMP platforms. This component is commonly replaced due to wear or breakage and may also be required when configuring compliant magazine release systems where...HKP-02159$19.95 -
HK91, G3 Trunnion - Used
H&K Heckler & Koch
$39.95HK German HK G3 & HK 91 Trunnion - Used These trunnions are from demilled G3 parts kits and will have leftover receivers and barrel stubs installed along with factory barrel pins. Please note the picture shows one with the demilled parts removed...HKP-00718$39.95 -
HK MR556 A4 Upper Receiver Kit - 16.5″ - 5.56 - M-LOK
H&K Heckler & Koch
$1,939.00H&K MR556 A4 16.5″ 5.56 M-LOK Upper Receiver Kit This kit includes a complete upper receiver/barrel assembly, allowing Mil-Spec 5.56mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system. This system utilizes a piston...HKP-21909$1,939.00 -
HK MR556 A4 Upper Receiver Kit - 11"- M-LOK
H&K Heckler & Koch
$1,998.95H&K Heckler & Koch MR556 Upper Receiver Kit A4 -11″ - M-LOK This kit includes a complete upper receiver/barrel assembly, allowing Mil-Spec 5.56mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system. This...HKP-21910$1,998.95 -
HK G36, SL8 Magazine Paddle Release
USA
$17.95US HK G36 and HK SL8 Magazine Paddle Release HK G36 Mag Release or mag catch. Compatible With: HK SL8 HK G36 HK G36K HK G36CHKP-18222$17.95 -
HK MP5K, SP89, SP5K Trunnion - 9mm - RS
RCM
$69.95MP5K Reverse Stretch Trunnion US-made to exact factory HK specifications for the HK MP5K, SP89 9mm builds. There is a difference between the MP5K and the MP5 trunnion. This offering is the correct trunnion for the MP5K and all MP5K PDW variants,...HKP-02242$69.95 -
HK417, MR762 Magazine Catch Spring
H&K Heckler & Koch
$9.95Heckler and Koch Magazine Catch Spring for HK417 and HK MR762 New HK German manufacture. Factory correct magazine catch for the magazine release. Compatible With: HK MR762 HK 417 HK G28HKP-16520$9.95