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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AR-15 Mil-Spec Buffer Tube Kit
HKP HK Parts
$42.95Mil-Spec Buffer Tube Kit Compatible With: AR-15 style platforms Not correct length for HK rifles Includes: Made with T7 7075 aircraft-grade aluminum Made in the USA with a polished inside tube Mil-Spec triple hard coat Teflon anodized...HKP-02735$42.95 -
HK G36 Backplate, Complete - Recoil Buffer and Assembly
USA
$84.95HK G36 Backplate Complete With Recoil Assembly New G36 Backplate with new G36/SL8 recoil buffer and recoil assembly. This assembly does include the recoil rod retaining screw. This is a great spare or replacement to have on hand. These are also required...HKP-18537$84.95 -
HK USC Magazine Release
H&K Heckler & Koch
$19.95Heckler and Koch .45 ACP Carbine Magazine Release for HK USC This is a great replacement as they are prone to breakage and wear. Please Note: For those that have a HK USC with a bullet button and are moving to a free state and want to revert back to the...HKP-02196$19.95 -
On Sale
HK MP5K Trunnion - 9mm
HKP HK Parts
Now: $36.94Was: $57.95HK MP5K Trunnion - USA US made to exact factory HK specifications for the HK MP5K type builds. Machined completely from ordnance grade steel and heat treated to factory specs. These are the best USA made trunnions on the market. Machined to HK spec...HKP-17964Now: $36.94Was: $57.95 -
On Sale
HK MP5, MP5K Rear Sight Base - Billeted
HKP HK Parts
Now: $11.44Was: $17.95HKP HK Parts Billeted Rear Sight Base - Weldment for HK MP5 and HK MP5K All steel HK MP5, MP5K billeted rear sight base. The most correct MP5, MP5K rear sight base available. The only billeted factory correct sight base with the factory HK German side...HKP-18087Now: $11.44Was: $17.95 -
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 -
HK416, MR556, HK417, MR762 Takedown Pin - Rear - A4 Style
H&K Heckler & Koch
$47.95H&K MR556, HK416, HK417, MR762 Rear Takedown Pin Factory A4 rear takedown pin. Will work for A1 and A4 applications. Compatible With: HK MR556 A1 and A4 HK416 HK MR762 A1 and A4 HK417 AR-14, M4, M16HKP-22029$47.95 -
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 -
HK21, FMP21 Teardrop Rail Set - T-Rail
HKP HK Parts
$197.95HKP HK21/FMP21 Teardrop Rail Set HK teardrop style reinforcement rails. The ultimate choice for period correct builds. Expertly crafted in the USA from high-quality 4140 steel, these ready-to-weld rails are engineered for precision and durability...HKP-21671$197.95 -
Out Of Stock
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 -
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