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 Rear Sight Base
HKP HK Parts
$19.95HKP HK Parts Rear Sight Base - Weldment for HK MP5 and HK MP5K The only factory-correct sight base with the factory HK German side axis grooves. Compatible With:HKP-02450$19.95 -
HK G36 Backplate Complete with Recoil Assembly
H&K Heckler & Koch
$199.95HK G36 Backplate Complete With Recoil Assembly New HK German G36 Backplate with new G36/SL8 recoil buffer and recoil assembly. This assembly does include the recoil rod retaining screw. This is a...HKP-16735$199.95 -
Out Of Stock
HK MR556, MR223 Upper Receiver - Forward Assist and Ejection Door
H&K Heckler & Koch
$694.95New HK German Partially Pre-Assembled Upper Receiver for HK MR556 and HK MR223 Each unit comes just as shown with the F/A (forward assist) assembly and ejection port door assembly installed from the...HKP-16950$694.95 -
Out Of Stock
HK MP5, MP5K Case Deflector
H&K Heckler & Koch
$0.00HK German case deflector for receiver flat or receiver for all MP5, HK94, MP5K & SP89 builds. The case deflector is riveted or welded in place on the ejection port of the 9mm receiver/flat to aid in...HKP-00871$0.00 -
HK G28 Buffer Tube
H&K Heckler & Koch
$224.99Heckler and Koch HK G28 Buffer Tube / Receiver Extension New HK German buffer tube with the proper slot cut for use with the G28 stock. This is the factory correct part needed to get the full range...HKP-16741$224.99 -
HK91, G3 Magazine Catch - Used
H&K Heckler & Koch
$16.95Heckler and Koch Magazine Catch, USED for HK91, HK G3, and PTR91 The highest quality magazine catch available. High quality HK German production units are slightly used HK Parts from Heckler and Koch...HKP-18693$16.95 -
HK417, MR762, G28 Ejection Port Cover Axle Spring
H&K Heckler & Koch
$9.95H&K HK MR762/417/G28 Ejection Cover Axle Spring New Hk German manufacture for the MR762 & HK 417 firearm. The spring is used on the axle and ejection port cover door to allow it to be closed and...HKP-16753$9.95 -
HK MP5 Lower Receiver - Section
H&K Heckler & Koch
$54.95HK MP5 Rear Receiver Section HK German demilled receiver section with rear sight base as installed at the factory. The rear push pin section is still attached to the demilled receiver section.HKP-02147$54.95 -
Out Of Stock
HK416 Upper Receiver Kit - 10.4" - 5.56
HKP HK Parts
$2,485.95HKP 416 10.4" 5.56 Complete Upper Kit Complete Each kit includes the complete upper assembly, bolt group, tungsten buffer, & high-reliability SS recoil spring. This upper kit is a complete gas piston...HKP-17662$2,485.95 -
HK416, MR556 Charging Handle Roll Pin
H&K Heckler & Koch
$7.95HK Heckler and Koch Clamping Sleeve or Roll Pin for Pawl on Charging Handles This is the longer one that is used on the outside of the charging handle. There are one of these pins used per charging...HKP-17063$7.95 -
HK416 OTB E1 Buttstock and Buffer Tube Set
H&K Heckler & Koch
$469.95H&K MIL-SPEC 416 OTB Buffer Tube & HK E1 Stock Combo Genuine HK416 E1 Stock with the new style marine environment "over the beach" buffer tube. Buffer tube has ball bearing rollers to tighten the...HKP-20104$469.95 -
HK416, MR556 Charging Handle Release Latch
H&K Heckler & Koch
$39.95Heckler and Koch HK MR556/416 Charging Handle Release Latch Perfect replacement item for the MR556 and HK 416 charging handle. New HK German manufacture. These can become chewed up and damaged with a...HKP-16553$39.95