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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HK33, HK93, HK51, HK91, G3 Paddle Mag Release - Standard
H&K Heckler & Koch
$8.95New HK German Paddle Magazine Release This item is a brand new H&K genuine part, not a used or surplus part. It's used for installation on all HK .223 & .308 HK rifles. Compatible With: HK 91 HK G3 HK 51 HK 93 HK 33 HK PSG-1 HK MSG-90HKP-01851$8.95 -
HK 90 Series Paddle Mag Release - Easy Install Fixture
HKP HK Parts
$187.95HKP 90 Series Paddle Mag Release Easy Install Fixture The original one and only paddle mag release fixture. The perfect jig for the installation of the factory correct paddle mag release with the proper hole placement and an easy to use jig that will...HKP-17587$187.95 -
HK MP5, MP5K Scope Tab - Weldment
HKP HK Parts
$9.95MP5, MP5K Sight Tab - Weldment HK MP5, MP5K 17-4 Stainless H900 rear sight tab. The most correct MP5, MP5K rear sight base available. If you want your build to look as factory correct as possible then this sight base is an absolute must. Compatible...HKP-17503$9.95 -
Out Of Stock
HK SP5K Mag Release Upgrade Kit - 9mm - Drop In Paddle
HKP HK Parts
$74.95HK SP5K Anti-Rattle Roller Tipped "Paddle" Magazine Release Install Kit No modifications, no refinishing...complete drop-in kit included. New USA made busing for a drop-in install kit for the HK SP5K. This kit will allow any end-user to quickly,...HKP-18192$74.95 -
HK Full Auto Paddle Magazine Release Bushing HK German - Used
H&K Heckler & Koch
$4.95H&K Full Auto Paddle Magazine Release Bushing HK German - Used This part is for use in all 90-series H&K weapon systems. Used for installing a paddle mag release. Please Note: This is not for use on semi-auto HK builds. This part is used for...HKP-02303$4.95 -
On Sale
HK UMP, USC 9mm / .40 S&W / .45 ACP Enhanced Top Receiver Rail - BLEMISHED
HKP HK Parts
Now: $28.95Was: $49.95HKP H&K UMP/USC (.40 S&W/.45 ACP/9mm) Enhanced Top Receiver Rail - BLEMISHED COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE FINAL. The extended length allows...HKP-14541-BNow: $28.95Was: $49.95 -
HK416, MR556 Mil-Spec Enhanced Buffer Tube
H&K Heckler & Koch
$254.95HK 416 & MR556 OTB (over the beach) Buffer Tube/Receiver Extension Each mil-spec buffer tube has built-in drainage holes in the rear of the tube and also on the bottom to maximize efficiency. Each buffer tube has ball-bearing rollers to tighten the...HKP-02716$254.95 -
HK416A5 Castle Nut - Extended
H&K Heckler & Koch
$75.95H&K HK416 A5 Factory German Extended Castle Nut Original HK Factory German steel 416 A5 Extended Castle Nut. Perfect for MR556, HK 416 A5 builds, or upgrades.HKP-19164$75.95 -
HK416, HK417, MR556, MR762 Takedown Pin - Rear - A1 Style
H&K Heckler & Koch
$79.95H&K HK MR556/MR762/416/417 Rear Lower Receiver Locking Pin This is the rear takedown pin with ball detent and locking mechanism installed. The idea behind this type of system is to decrease the movement of the upper and lower receivers and improve...HKP-02672$79.95 -
Out Of Stock
HK416 E1, MR556 Charging Handle - Ambidextrous
H&K Heckler & Koch
$129.95H&K HK MR556/416 E1 Charging Handle - Ambidextrous HK's design boasts a smooth & easy to release latch with an enhanced oversized charging handle. Compatible With: HK MR556 HK 416 Other AR15, M4 & M16 applicationsHKP-01959$129.95 -
HK416, HK417, MR556, MR762 Detent Takedown Pin
H&K Heckler & Koch
$9.95H&K HK MR556/MR762/416/417 Detent Takedown Pin Factory H&K takedown pin for MR556 A4. Compatible With: HK MR556 HK 416 HK MR762 HK 417HKP-02540$9.95 -
AR-15 Buffer Tube Castle Nut
Ergo
$9.99Ergo AR-15 Castle Nut For Buffer Tubes - US Made Steel Castle-nut for AR buffer tubes fits both mil-spec and commercial buffer tubes alike. Compatible With: HK MR556 & 416 AR-15 style platformsHKP-02729$9.99