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 Magazine Release Lever Spring - 10mm and .40 S&W
H&K Heckler & Koch
$9.95H&K MP5 40/10 Magazine Release Lever Spring The needed spring that fits in the mag release lever and the magwell for the MP5 40/10 series. Made in Germany and no longer offered or made. These units are the latest design with the ground ends for...HKP-18109$9.95 -
HK MP5K Trunnion - 9mm
HKP HK Parts
$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-17964$57.95 -
HK MP5, MP5K Rear Sight Base - Billeted
HKP HK Parts
$17.95Billeted MP5, MP5K Rear Sight Base - Weldment 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 axis grooves. If you want...HKP-18087$17.95 -
HK Mil-Spec Buffer Tube Kit
HKP HK Parts
$42.95Mil-Spec Buffer Tube Kit Compatible With: HK MR556 & 416 AR-15 style platforms Includes: Made with T7 7075 aircraft-grade aluminum Made in the USA with a polished inside tube Mil-Spec triple hard coat Teflon anodized finish Each unit comes with a...HKP-02735$42.95 -
HK416, MR556 Buffer Tube - Enhanced
H&K Heckler & Koch
$199.95FDE HK 416, MR556 OTB (over the beach) Buffer Tube, Receiver Extension - Commercial Genuine HK German manufactured 416 & MR556 latest generation, marine environment & over the beach buffer tube. Each commercial buffer tube has built in drainage...HKP-18499$199.95 -
Picatinny Rail for HK Receivers - 5.3" - 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 MP5, MP5K Contact Piece for Paddle Mag Release - 9mm
H&K Heckler & Koch
$59.95MP5, MP5K 9mm Contact Piece For Paddle Mag Release - 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 With: MP5, SP5, 94, SP5 MP5K, SP5K,...HKP-00118$59.95 -
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 -
$19.95 -
HK91, G3 Magazine Catch
H&K Heckler & Koch
$19.95G3 Magazine Catch High-quality HK German production units are brand-new. These also have the proper newer style cut in them and round shafts. Compatible With: HK G3 HK91 PTR91HKP-02073$19.95 -
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 -
HK416, HK417, MR556, MR762 Bridge
H&K Heckler & Koch
$24.95H&K HK 416/417/MR556/MR762 Bridge For Lowers Compatible With: HK MR556 HK 416 HK MR762 HK 417HKP-02676$24.95