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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On Sale
HK416A5 Stripped Upper Receiver
H&K Heckler & Koch
Now: $440.99Was: $489.99HK 416A5 - Stripped Upper Receiver This is the factory correct receiver for a true 416 build as it features the M16 relief cut in the bottom, rear portion of the receiver (shown in last pricture). Compatible With: HK 416 HK MR223 HK MR556 Need a...Now: $440.99Was: $489.99 -
Out Of StockOn Sale
HK MP5, MP5K Contact Piece for Paddle Mag Release - 9mm
H&K Heckler & Koch
Now: $53.96Was: $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,...Now: $53.96Was: $59.95 -
On Sale
HK91, G3 Trunnion - Used
H&K Heckler & Koch
Now: $35.96Was: $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...Now: $35.96Was: $39.95 -
On Sale
HK416 E1, MR556 Charging Handle - RAL8000
H&K Heckler & Koch
Now: $152.99Was: $169.99New RAL 8000 HK Designed HK416, MR556 Ambidextrous Charging Handle (E1). The E1 HK 416 FDE charging handle release latch has the ability of being swapped from the left side (E1) to the right sight (E2) with simple tools. HK's own design boasts a smooth...Now: $152.99Was: $169.99 -
On Sale
HK416, HK417, MR556, MR762 Bridge
H&K Heckler & Koch
Now: $22.45Was: $24.95H&K HK 416/417/MR556/MR762 Bridge For Lowers Compatible With: HK MR556 HK 416 HK MR762 HK 417Now: $22.45Was: $24.95 -
Out Of StockOn Sale
MR556 A4 Upper Receiver Kit - 16.5″ - 5.56 - M-LOK
H&K Heckler & Koch
Now: $1,616.36Was: $1,939.00H&K MR556 A4 16.5″ 5.56 M-LOK Upper Receiver Kit This kit includes a complete upper receiver/barrel assembly, allowing Mil-Spec 5.56mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system. This system utilizes a piston...Now: $1,616.36Was: $1,939.00 -
On Sale
HK G36, SL8 Pin - Axle - Cocking Handle
H&K Heckler & Koch
Now: $10.75Was: $11.95HK German G36 & SL8 Cocking Handle Axle Pin This is the rivet pin that is used to attach the swiveling cocking handle to the body of the carrier. These can be replaced as they break and wear. Compatible With: HK G36 HK SL8Now: $10.75Was: $11.95 -
On Sale
HK21, FMP21 Teardrop Rail Set - T-Rail
HKP HK Parts
Now: $158.36Was: $197.95HKP HK21/FMP21 Teardrop Rail Set HK teardrop style reinforcement rails. The ultimate choice for period correct builds. Expertly crafted in the USA from high-quality 4140 steel, these ready-to-weld rails are engineered for precision and durability...Now: $158.36Was: $197.95 -
On Sale
HK93 Trunnion
RCM
Now: $58.50Was: $65.00RCM HK93 Trunnion Made to exact factory HK specifications for the HK93, HK33 type builds. These are the best trunnions of their kind on the market. Machined to HK spec making the install painless and hassle free. The way a custom HK build it should...Now: $58.50Was: $65.00 -
On Sale
HK MP5K, SP89, SP5K 9mm RS Trunnion
RCM
Now: $62.96Was: $69.95MP5K Reverse Stretch Trunnion US-made to exact factory HK specifications for the HK MP5K, SP89 9mm builds. There is a difference between the MP5K and the MP5 trunnion. This offering is the correct trunnion for the MP5K and all MP5K PDW variants,...Now: $62.96Was: $69.95 -
On Sale
MP5K Complete Weldment Set
Now: $53.96Was: $59.95MP5K Complete Weldment Set Each set of weldments is all of the weldments required for an MP5K flat. Includes: Rear sight base Sight tab Case deflector Semi auto shelf Side reinforcement tabs 2 X rear stock bushingsNow: $53.96Was: $59.95 -
Out Of StockOn Sale
MR556 Upper Receiver Kit -16.5" - M-LOK
H&K Heckler & Koch
Now: $1,601.96Was: $1,779.95New HK Factory German MR556 Upper Kit with M-LOK forearm Includes: Complete MR556 upper receiver with M-LOK forearm MR556 Bolt group Complete Tungsten Filled HK Buffer HK Buffer Spring One 30 Round HK Steel Maritime Magazine No FFL required as the...Now: $1,601.96Was: $1,779.95