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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HK416, MR556 Piston Guide - Threaded - Upper Receiver
H&K Heckler & Koch
$19.95HK MR556 & 416 Upper Receiver Threaded Piston Guide Compatible With: HK MR556 HK 416 HK M27HKP-02640$19.95 -
Out Of Stock
HK Semi Auto Shelf, Hanger Block For Receiver
HKP HK Parts
$13.95HK Semi Auto Shelf Weldment, Hanger Block Weldment HK Semi Auto Shelf, Hanger Block to HK's factory specifications for c/p trigger housings. Weld on shelf that is the needed receiver block that welds to the rearward portion of the magwell to allow the...HKP-17572$13.95 -
HK MP5K, SP5K Rear Push Pin Weldment Set
USA
$14.95HK MP5K, SP5K Rear Push Pin Weldment Set This weldment set is the 2 pieces needed for the rear of the flat/receiver that holds the stock/brace or end cap in place. CNC machined from weldable steel and the finest weldment available on the market...HKP-19632$14.95 -
HK417, MR762, G28 Castle Nut for Buffer Tube - Extended
H&K Heckler & Koch
$85.95HK G28 Buffer Tube Castle Nut New HK German G28 castle nut for the HK MR762, HK417 & G28 models. Black in color. This is the proper part for use with the G28 buffer tube and stock upgrades. Compatible With: HK MR762 HK 417 HK G28 DMRHKP-16763$85.95 -
HK416, HK417, MR556, MR762 Forward Assist Plunger Spring
H&K Heckler & Koch
$5.95H&K HK MR556/MR762/416/417 Forward Assist Plunger Spring New HK German manufacture. Compatible With: HK MR556 HK 416 HK MR762 HK 417 HK G28 HK M27HKP-02537$5.95 -
HK416, MR556 Ejector Port Cover Pin
H&K Heckler & Koch
$19.95HK MR556 & 416 Ejector Port Cover Pin Compatible With: HK MR556 HK 416HKP-02661$19.95 -
HK G36 Backplate
H&K Heckler & Koch
$94.99HK G36 Backplate With Recoil Buffer This is a great spare or replacement to have on hand. These are also required for those that are doing the SL8-G36 conversions provided by Tommy Bostic & Chopstix Kid.HKP-01058$94.99 -
HK MP5 Receiver Flat - 9mm
HKP HK Parts
$189.95HKP HK MP5 9mm Receiver Flat New MP5 receiver flat made by the original German tool and die maker of the LSC receiver flat utilizing factory original German prints and specifications. The creator of our receiver flat has been regarded as the premier flat...HKP-20921$189.95 -
HK91, G3, HK33, HK53, HK93 Contact Piece for Paddle Mag Release
H&K Heckler & Koch
$29.95HK .223/556 & 308 Contact Piece For Paddle Magazine Release German HK manufacture. The contact piece is used in the magazine release assembly for the paddle mag release. Compatible With: HK 33, 53, 93 HK G3, 91, PTR91HKP-00465$29.95 -
HK MP5K, SP89 Receiver Flat with Weldment Set
HKP HK Parts
$239.95HKP - MP5K, SP89 Receiver Flat With Weldment Set New MP5K receiver flat and weldment set combined for the best complete build option on the market. Made by the original German tool and die maker of the LSC receiver flat utilizing factory original German...HKP-20882$239.95 -
HK UMP, USC Magazine Release Spring
H&K Heckler & Koch
$9.95HK UMP & USC Magazine Release Spring HK German factory mag release spring for all USC and UMP mag releases. Compatible With: USC lowers UMP lowersHKP-01899$9.95 -
HK USC Magazine Release - .45 ACP
H&K Heckler & Koch
$19.95H&K USC (.45 ACP) Carbine Mag Release This is a great replacement as they are prone to breakage & wear. Please Note: For those that have a USC with a bullet button and are moving to a free state and want to revert back to the...HKP-02196$19.95