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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Out Of Stock
HK416, MR556 Ejection Port Cover Door Assembly
H&K Heckler & Koch
$89.95HK German HK 416, MR556 Ejection Port Cover Door Assembly Complete This is the newer polymer style cover found on the latest HK 416 and MR556's. This is the complete ejection port door assembly needed on all AR15 or MR556/HK416 models. Can also be used...$89.95 -
HK416, MR556 Castle Nut
H&K Heckler & Koch
$32.95H&K HK MR556/416 Castle Nut For Buffer Tube New HK German manufacture. This buffer tube castle nut will fit both mil-spec and commercial buffer tubes. All steel manufacture. With HK round tool attachment points as well as traditional wrench...$32.95 -
HK MP5 1913 End Plate Adapter
MI Midwest Industries
$89.95MI HK MP5 1913 End Plate Adapter The Midwest Industries Picatinny end plate adapter opens up your stock and brace options to a myriad of off-the-shelf possibilities. The adapter installs in the same manner as the factory end cap with a single push pin...$89.95 -
HK MP5F Receiver Flat - Alternate Holes
HKP HK Parts
$125.95HKP HK MP5F 9mm Flat - Alternate Holes MP5 receiver flat crafted by the original German tool and die maker of the LSC receiver flat using factory original German prints and specifications. This receiver features alternate holes for the correct MP5F or...$125.95 -
HK33, HK53, HK93 Receiver Flat - Complete Weldment Set
HKP HK Parts
$229.95HK .223, 556, & 300 BLK Receiver Flat With Complete Weldment Set Combo Each flat and weldment set comes with 223/556/300BLK complete as a builders combo ready to assemble. Compatible With: HK93, HK33, & HK53 Style Builds 300...$229.95 -
Picatinny Rail for HK Receivers - 15 Slot
DTAC Dakota Tactical
$74.95Dakota Tactical Picatinny Rail To Weld To The Receiver 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...$74.95 -
HK MR556 Incomplete Upper Receiver
H&K Heckler & Koch
$449.95HK German Stripped HK MR556 Upper Receiver New factory German incomplete and unmarked MR556 upper receiver. Compatible With: HK MR556 HK MR223 HK 416 Do you need a matching lower for your build? STS416 A5 LOWER - Specialized Tactical...$449.95 -
HK21, HK11 Trunnion
RCM
$274.95RCM HK21 Trunnion When RCM set out to make a replacement trunnion for the venerable HK21, they started the process by putting a factory unit through rigorous destructive metal testing. The end-product: a US-made trunnion blending the proper...$274.95 -
HK416, MR556, MR762 Forward Assist Assembly
H&K Heckler & Koch
$74.95H&K HK MR556/MR762/416 Forward Assist Assembly H&K Germany factory MR556 & HK416 forward assist assembly complete. Compatible With: HK MR556 HK 416 HK MR762$74.95 -
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...$13.95 -
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 M27$19.95 -
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 M27$5.95