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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H&K HK MR556/416 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...HKP-16951$89.95 -
H&K HK MR556 Front Lower Receiver Locking Pin
H&K Heckler & Koch
$64.95H&K HK MR556 Front Lower Receiver Locking Pin With Spring Loaded Detent This part is the front (large) 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...HKP-02663$64.95 -
Tac Latch - PTR Spec
$69.95Tac Latch (latest Generation) PTR Spec - PTR .308 Firearms The new updated style of Tac latch is made specifically for the PTR 91 .308 receiver and will require very little modification to the firearm for installation. A major overhaul of the existing...HKP-17611$69.95 -
Out Of Stock
HKP 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 -
HKP HK MP5F 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...HKP-21551$125.95 -
HKP HK MP5K QD End Cap with Buffer - Black
HKP HK Parts
$44.95Quick Detach MP5K, SP-89 Steel End Cap With Replaceable Rubber Buffer Compatible With: MP5K SP89 Clone or other custom buildsHKP-20117$44.95 -
H&K MP5K/SP89/SP5K 9mm End Cap
H&K Heckler & Koch
$99.95HK Factory German MP5K, SP-89, & SP5K End Cap With Sling Swivel Each pistol end cap is OEM HK German MP5K and MP5K-N and has the HK German factory buffer. Compatible With: MP5K SP89 SP5K MP5K-N MP5K-PDW MP5K Clone Or Other Custom BuildsHKP-00394$99.95 -
$49.95 -
DTAC 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...HKP-17819$74.95 -
HKP MP5 End Cap with Sling Swivel
HKP HK Parts
$84.95HK Alloy Pistol End Cap with Sling Swivel Made from solid billet aircraft grade aluminum with the HK German sling loop and rubber heavy duty H buffer. With the alloy construction this unit will not break like the plastic end caps. Compatible...HKP-18138$84.95 -
RCM 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...HKP-21609$274.95 -
H&K HK G36 Backplate w/ Recoil Buffer
H&K Heckler & Koch
$79.95HK 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$79.95 -
H&K HK MR556 Incomplete Upper Receiver
H&K Heckler & Koch
$399.95HK 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...HKP-02615$399.95 -
H&K HK MR556/MR762/416 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 MR762HKP-16528$74.95 -
HKP HK 93/53/33 (5.56/.223) Receiver Flat With 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...HKP-00006$229.95 -
HKP MP5K/SP89/SP5K 9mm End Cap - HK Style
HKP HK Parts
$64.95HKP MP5K/SP89/SP5K 9mm End Cap - HK Style This end cap is an identical reproduction of the factory end cap and features the original HK style buffer. Compatible With: MP5K SP5K SP89 In spec. clones and custom buildsHKP-16135$64.95 -
HKP MP5 40/10 Receiver Flat
HKP HK Parts
$399.95MP5 40 & MP5 10mm Receiver Flat - USA The new and latest production with the weldment locations is already lasered and ready to go. This flat is the finest available for the MP5 40/10 family of firearms. Compatible With: MP5 .40 Cal MP5 10mm MP5 ...HKP-00767$399.95 -
Out Of Stock
H&K MP5K Replacement Buffer For Factory End Cap or Folding Stock
H&K Heckler & Koch
$24.95H&K MP5K Replacement Buffer for Factory End Cap or Folding Stock This item is a Heckler & Koch Genuine Part, used to replace the factory HK buffer on MP5K folding stocks and end caps. This is only usable on the factory OEM stock and end cap. This...HKP-01233$24.95 -
Out Of Stock
H&K HK MR556/416 Upper Receiver Threaded Piston Guide
H&K Heckler & Koch
$19.95HK MR556 & 416 Upper Receiver Threaded Piston Guide Compatible With: HK MR556 HK 416 HK M27HKP-02640$19.95 -
HKP MP5, MP5K Rear Sight Base - Billeted
HKP HK Parts
$17.95Billeted MP5, MP5K Rear Sight Base - Weldment All steel HK MP5, MP5K billeted rear sight base. The most correct MP5, MP5K rear sight base available. The only billeted factory correct sight base with the factory HK German side axis grooves. If you want...HKP-18087$17.95 -
HKP MP5K 9mm Trunnion
HKP HK Parts
$57.95HK MP5K Trunnion - USA US made to exact factory HK specifications for the HK MP5K type builds. Machined completely from ordnance grade steel and heat treated to factory specs. These are the best USA made trunnions on the market. Machined to HK spec...HKP-17964$57.95 -
HKP HK MP5 9mm Receiver Flat
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 -
Choate MP5K/SP89 9mm Steel End Cap W/ Buffer
Choate
$45.95MP5K & SP-89 Steel End Cap With Replaceable Rubber Buffer Fits perfectly on all HK MP5K-type builds or projects. All metal construction, so you know it will last. Each unit comes with a sling loop for use with multiple sling types. Compatible...HKP-00395$45.95 -
H&K (5.56/.223) & (7.62x51/.308) 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 -
DTAC Picatinny Rail For HK Receivers - 13 Slot
DTAC Dakota Tactical
$74.95DTAC Picatinny Rail For HK Receivers - 13 Slot 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 With: HK...HKP-17818$74.95 -
H&K HK MR556/MR762/416/417 Forward Assist Plunger Spring
H&K Heckler & Koch
$9.95H&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$9.95 -
HK G36 Backplate Complete w/ Recoil Assembly
USA
$84.95HK G36 Backplate Complete With Recoil Assembly New G36 Backplate with new G36/SL8 recoil buffer and recoil assembly. This assembly does include the recoil rod retaining screw. This is a great spare or replacement to have on hand. These are also required...HKP-18537$84.95 -
Choate HK MP5 QD End Cap with Buffer - Black
HKP HK Parts
$99.95Quick Detach Steel End Cap With Replaceable Rubber Buffer - HK MP5 With this MP5 QD end cap upgrade you will get a heavier buffer to internally protect your firearm and keep your bolt carrier in tip top condition for years to come. Machined aircraft...HKP-20118$99.95 -
HKP - 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 G36 Backplate w/ Recoil Buffer
USA
$44.95HK G36 Backplate With Recoil Buffer New G36 Backplate with new G36/SL8 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...HKP-18538$44.95 -
Out Of Stock
H&K HK MR556/416 Ejector Port Cover Pin
H&K Heckler & Koch
$14.95HK MR556 & 416 Ejector Port Cover Pin Compatible With: HK MR556 HK 416HKP-02661$14.95 -
HKP HK 416 11.5" 5.56 Complete Upper Receiver Assembly
HKP HK Parts
$2,485.95HKP HK 416 11.5" 5.56 Complete Upper Kit Complete HKP 416 style complete upper assembly. This top-tier assembly seamlessly fits onto your mil-spec lower or a STS 416 lower, providing the perfect solution for those seeking an 11.5" 416 style upper without...HKP-21539$2,485.95 -
H&K G3/91 Trunnion- Used
H&K Heckler & Koch
$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...HKP-00718$39.95 -
Out Of Stock
HKP 416 10.4" 5.56 Complete Upper Receiver Assembly
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 HK 416 style upper assembly that will drop on your...HKP-17662$2,485.95 -
H&K HK 416A5 Stripped Upper Receiver - Black
H&K Heckler & Koch
$599.95HK 416A5 - Stripped Upper Receiver - Black 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...HKP-18786$599.95 -
H&K HK MP5 Rear 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 -
RCM HK93 Trunnion
RCM
$64.95RCM 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...HKP-20807$64.95 -
RCM MP5K/SP89/SP5K 9mm RS Trunnion
RCM
$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,...HKP-02242$69.95 -
HKP MP5, MP5K Rear Sight Base
HKP HK Parts
$19.95MP5 & MP5K Rear Sight Base- Weldment The only factory-correct sight base with the factory HK German side axis grooves. Compatible With: HK MP5, 94 HK MP5K, SP89 HK MP5 40, MP5 10 MAC-5 clones may require custom fitment. Modified components are...HKP-02450$19.95 -
H&K HK 416/417/MR556/MR762 Bridge
H&K Heckler & Koch
$16.95H&K HK 416/417/MR556/MR762 Bridge For Lowers Compatible With: HK MR556 HK 416 HK MR762 HK 417HKP-02676$16.95