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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HKP 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 -
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 -
$49.95 -
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 -
H&K HK MR556/MR762 Front Lower Receiver Locking Pin
H&K Heckler & Koch
$59.95HK MR556 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 lower receivers and improve...HKP-02663$59.95 -
Out Of Stock
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 -
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 -
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 -
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 -
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 -
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 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
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 -
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 -
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 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 -
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 -
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 -
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 -
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 -
Out Of Stock
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 -
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 -
Out Of Stock
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 -
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 -
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 -
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 -
Out Of Stock
HKP HK 416C 9" Complete Upper Receiver Assembly
HKP HK Parts
$2,799.95HK416C Complete Upper Kit - 9" After years trying to get these back in. We finally bring you a rare unicorn of a find. With our complete 416c upper kit all that would be needed to complete this kit would be a mil-spec lower or a STS 416c lower...HKP-21042$2,799.95 -
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 -
H&K HK G36 Backplate Complete w/ Recoil Assembly
H&K Heckler & Koch
$199.95HK G36 Backplate Complete With Recoil Assembly New HK German 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...HKP-16735$199.95 -
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 -
Out Of Stock
H&K HK MR556/MR223 Upper Receiver w/ F/A & Ejection Door
H&K Heckler & Koch
$694.95New HK German Partially Pre-Assembled MR556/MR223 Upper Receiver Each unit comes just as shown with the F/A (forward assist) assembly and ejection port door assembly installed from the HK factory. Compatible With: HK MR556 HK MR223 HK...HKP-16950$694.95 -
H&K HK MR762, 417, G28 Ejection Cover Axle Spring
H&K Heckler & Koch
$9.95HK417, MR762 Ejection Cover Axle Spring New Hk German manufacture for the MR762 & HK 417 firearm. The spring is used on the axle and ejection port cover door to allow it to be closed and spring open. Compatible With: MR762 HK 417 G28HKP-16753$9.95 -
H&K G36/SL8 (5.56/.223) Factory Recoil Buffer
H&K Heckler & Koch
$20.95HK G36 Or SL8 Factory Recoil Buffer A critical spare part as these buffers deteriorate with usage and time.HKP-00290$20.95 -
H&K HK MP5 Rear Receiver Section
H&K Heckler & Koch
$24.95HK 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$24.95 -
H&K HK MR762 Lower Receiver Front Locking Pin - Black
H&K Heckler & Koch
$39.95H&K HK MR762 Lower Receiver Front Locking Pin - Black This 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 lower receivers and...HKP-16602$39.95 -
On Sale
HKP - ACR to SP5K Adapter - BLEMISHED
HKP HK Parts
Now: $79.95Was: $139.95HKP - ACR TO SP5K Adapter - BLEMISHED COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE FINAL. We now offer the best option to convert the ACR Stock to be compatible with...HKP-20844-BNow: $79.95Was: $139.95 -
H&K HK MR556/MR762/416/417 Bridge
H&K Heckler & Koch
$16.95HK German Bridge For HK416, HK417, MR556, & MR762 LowersHKP-02676$16.95 -
H&K MP5 & SP5 A1 End Cap With Sling Swivel
H&K Heckler & Koch
$139.99HK German MP5 & SP5 A1 End Cap With Sling Swivel The MP5 end cap allows the user to add a single-point sling. Perfect for a pistol build or a lower profile setup. Made by HK Germany. Compatible With: HK MP5 HK SP5 HK94 MP5 clones and other...HKP-00114$139.99 -
H&K HK G36/SL8 Complete Recoil Rod Assembly
H&K Heckler & Koch
$49.95Recoil Rod Assembly for HK G36 & SL8 New HK factory German G36/SL8 (fits all variants of SL8/G36) recoil rod assembly complete. Great for replacement or for a spare as these have been hard to find.HKP-01057$49.95 -
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