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 MR762/417/G28 Ejection Cover Axle Spring
H&K Heckler & Koch
$9.95H&K HK MR762/417/G28 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: HK MR762 HK 417 HK...HKP-16753$9.95 -
Out Of Stock
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 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 -
RCM HK PSG1 Style Trunnion
RCM
$119.95HK PSG1 Trunnion- PTR- USA RCM trunnion for custom PSG1, MSG90, & other custom HK91/G3 type builds. Machined completely from ordnance grade 9310 enhanced steel and heat treated to exact HK specifications. This item is the best USA made trunnion on...HKP-20522$119.95 -
HKP HK MP5 Receiver Flat - Smooth Top
HKP HK Parts
$125.95HKP HK MP5 Receiver Flat - Smooth Top The MP5 receiver flat has been meticulously crafted by the original German tool and die maker of the LSC receiver flat, utilizing factory original German prints and specifications. This receiver boasts a flat top,...HKP-21552$125.95 -
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 -
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 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 -
HKP MP5 40/10 Trunnion
HKP HK Parts
$139.95MP5 40 & MP5 10mm Trunnion Machined from ordnance-grade steel and heat-treated to factory specs. Each has the bullet guides pre-installed and included. These are the best USA-made trunnions on the market. Machined to HK spec, making the installation...HKP-02737$139.95 -
H&K HK MR762/417 Complete Buffer
H&K Heckler & Koch
$129.95H&K HK MR762/417 Complete Buffer Specifications: Weight: 6.1 Oz Overall length: 3.20" OD: 1.18" Compatible With: HK MR762 HK 417HKP-16769$129.95 -
Out Of Stock
HKP HK MP5K/SP89 9mm Flat Receiver
HKP HK Parts
$199.95MP5K, SP89 Receiver Flat - 9mm New MP5K 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...HKP-20733$199.95 -
H&K MR223 A3 Lower Parts Kit
H&K Heckler & Koch
$695.95H&K MR223 A3 Lower Parts Kit Factory HK lower parts kit for the MR223/556 platform—the ultimate choice for those seeking genuine factory German lower internal parts. This kit is essential for anyone looking to build an authentic 416A5 with...HKP-21811-M$695.95 -
HKP HK21/FMP21 Teardrop Rail Set
HKP HK Parts
$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...HKP-21671$197.95 -
H&K MP5 Rear Receiver Section
H&K Heckler & Koch
$14.95H&K MP5 Rear Receiver Section HK German demilled receiver section with rear sight base as installed at the factory. MP5 & HK94 Factory HK rear sight bases (portion welded to MP5 receiver), you get the actual demilled section of an MP5 receiver...HKP-02167$14.95 -
H&K HK MR762/417/G28 Receiver End Plate
H&K Heckler & Koch
$24.95H&K HK MR762/417/G28 Receiver End Plate New HK German factory. Compatible With: HK MR762 HK 417 HK G28HKP-16610$24.95 -
Out Of Stock
H&K HK MR762/417 Flush Cup QD End Plate - Black
H&K Heckler & Koch
$138.95H&K HK MR762/417 Flush Cup QD End Plate - Black Factory HK flush end cap with dual QD sockets for ambidextrious sling attachment. Compatible With: HK MR762 HK 417HKP-21642$138.95 -
HKP MP5K 40/10 Receiver Flat
HKP HK Parts
$199.95MP5K-40, MP5K-10 Receiver Flat - USA Receiver Flat for use with a MP5K-40 or MP5K-10mm build. Please note: This is for the flat as picture no weldments are included. ***This US made receiver flat counts as one required 922r compliant part***HKP-18033$199.95 -
Out Of Stock
H&K 416A5 RAL 8K Stripped Upper Receiver
H&K Heckler & Koch
$0.00HK German Un-Assembled Stripped HK 416A5 Upper Receiver - RAL 8K Brand new factory German RAL 8000 416A5 upper receiver. Compatible With: HK MR556 HK MR223 HK 416 Looking for a matching lower for your build? STS416 A5 LOWER - Specialized Tactical...HKP-18787$0.00 -
H&K HK MR762 Ejection Door Clamping Sleeve
H&K Heckler & Koch
$4.95H&K HK MR762 Ejection Door Clamping Sleeve Compatible With: HK MR762HKP-16518$4.95 -
Out Of Stock
HKP HK 416 Upper Receiver
HKP HK Parts
$489.95US Made Complete HK 416, MR556 Style Upper Receiver New US made HK416/MR556 style upper receiver. Includes: Upper receiver Forward assist assembly Ejection port door assembly Piston guide Compatible With: HK MR556 HK MR223 HK 416 Need a...HKP-17783$489.95 -
HKP V51 Backplate
HKP HK Parts
$167.95HKP V51 Backplate HK Parts brings you a long lost part that was no longer available till now. The Vector Arms V51 firearms was one of the most aclaimed PDW of its time but replacement parts have become difficult to source. We now take like new G3...HKP-21201$167.95 -
H&K HK MR762/417 Cylindrical Pin For Stop Pin
H&K Heckler & Koch
$9.95H&K HK MR762/417 Cylindrical Pin For Stop Pin HK 2x18 mm pin designed for use with the rear take down pin detent and spring. Compatible With: HK MR762 HK 417HKP-16619$9.95 -
MM HK PSG1/21E/23E Forward Complete Assist Assembly
Michaels Machines
$679.95MM HK PSG1/21E/23E Forward Complete Assist Assembly Michael's Machines US-made complete forward assembly or your HK PSG1, MSG90, HK21E/23E. A great option for a build now that the factory units are no longer available. Available exclusively...HKP-00852$679.95 -
Out Of Stock
H&K 416 Front Takedown Pin
H&K Heckler & Koch
$49.95H&K 416 Front Takedown Pin The 416 front takedown pin is a German-made component designed to securely fasten the upper and lower receivers. Precision-machined for a proper fit, it ensures reliable function and serves as an ideal replacement or spare...HKP-21862$49.95 -
Out Of Stock
H&K MP5K/SP89/SP5K 9mm Incomplete End Cap
H&K Heckler & Koch
$0.00HK Factory German MP5K, SP-89, SP5K End Cap - Incomplete Each pistol end cap is OEM HK German MP5K, MP5K-N, SP5K, SP89 stripped end cap. Compatible With: MP5K SP89 SP5K MP5K-N MP5K-PDW MP5K clones or other custom buildsHKP-18208$0.00 -
Out Of Stock
HKP MP5, 94 Trunnion 9mm - USA
HKP HK Parts
$54.95HKP MP5, 94 Trunnion 9mm - USA US made to exact factory HK specifications for the HK MP5, 94 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...HKP-17934$54.95 -
Out Of Stock
MM HK PSG1/MSG90/91/G3 (7.62x51/.308) T-Rail Reinforcement Set For Receiver
Michaels Machines
$299.95HK Receiver Reinforcement T-Rail Set For Left and Right Sides T-rails are used to strengthen HK receivers or for custom builds. These are the finest T-rails available on the market. Made from enhanced steel and perfect for that custom HK project...HKP-00236$299.95 -
On Sale
Choate HK MP5 QD End Cap with Buffer - Black - BLEMISHED
HKP HK Parts
Now: $79.95Was: $99.95Choate HK MP5 QD End Cap with Buffer - Black - BLEMISHED COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE FINAL. With this MP5 QD end cap upgrade you will get a heavier...HKP-20118-BNow: $79.95Was: $99.95 -
H&K HK MR762/417 Ejection Port Cover
H&K Heckler & Koch
$42.95H&K HK MR762/417 Ejection Port Cover New HK German polymer .308 style MR762, HK 417 & G28 firearms. Compatible With: HK MR762 HK 417 HK G28 Other HK Spec .308 firearmsHKP-16598$42.95 -
HK 417 German Parts Kit w/ 12" Barrel
H&K Heckler & Koch
$26,000.00HK German 417 Assaulter 12" Parts Kit - Unfired The ultimate HK unicorn. Have you ever seen one let along seen a brand new German UNFIRED HK417 Assaulter parts kit with EVERY single part with the exception of the stripped lower? This is the ultimate HK...HKP-18433$26,000.00 -
Out Of Stock
HKP HK MP5K Receiver Flat - Smooth Top
HKP HK Parts
$129.95HKP HK MP5K Receiver Flat - Smooth Top The MP5K receiver flat has been meticulously crafted by the original German tool and die maker of the LSC receiver flat, utilizing factory original German prints and specifications. This receiver boasts a flat top,...HKP-21550$129.95 -
H&K HK MR762/417 Upper Receiver - Incomplete
H&K Heckler & Koch
$889.95H&K HK MR762/417 Upper Receiver - Incomplete This stripped upper receiver includes the insalled threaded piston guide bushing. Compatible With: HK MR762 HK 417HKP-16624$889.95 -
HKP HK 416, MR556 Upper Receiver Forging
HKP HK Parts
$88.95HKP HK 416 A1/A3, MR556 Upper Receiver Forging HK Parts' very own 416 upper receiver forging. This is the first time that these forgings have been made available to the public. Our receivers come with the ever popular Cerro Forge "keyhole" marking. Cerro...HKP-21008$88.95 -
On Sale
HKP MP5 40/10 Trunnion - BLEMISHED
HKP HK Parts
Now: $78.95Was: $139.95HKP MP5 40/10 Trunnion - BLEMISHED COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE FINAL. Machined from ordnance-grade steel and heat-treated to factory specs. Each has...HKP-02737-BNow: $78.95Was: $139.95 -
HKP QD End Cap with Buffer - SP5
HKP HK Parts
$99.95HK SP5 - Quick Detach End Cap With this SP5 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 grade aluminum and Cerakoted for the best...HKP-20757$99.95 -
HK G3 - FMP Early Type Demilled Front End
EBO
$99.95HK G3 - FMP Early Type Demilled Front End Early style G3 front end with no hanger. These are the perfect option for those doing custom builds. Good condition over all. Includes: Cocking tube Complete cocking handle assembly Trunnion Barrel pinHKP-20845$99.95 -
H&K 93/53/33 (5.56/.223) Rear Receiver Section
H&K Heckler & Koch
$79.95H&K 93/53/33 (5.56/.223) Rear Receiver Section Each rear receiver section is from a factory German HK 33/53 that was demilled and includes the welded on rear sight base and push pin bushing intact.HKP-16481$79.95 -
Out Of Stock
H&K HK MR556/MR223 A5 Incomplete Upper Receiver - Black
H&K Heckler & Koch
$0.00HK German Un-Assembled/Stripped HK MR556/MR223 A5 Upper Receiver Factory HK MR556 A5 upper receiver. This is the semi-auto MR556 variant. Compatible With: HK MR556 HK MR223 HK 416*** Need a matching lower for your build? STS416 A5 LOWER -...HKP-18785$0.00 -
Out Of Stock
H&K HK UMP Demilled Extended Rear Receiver Section
H&K Heckler & Koch
$0.00HK German Factory UMP Receiver Section - ExtendedThis is a demilled factory HK UMP rear receiver section that is perfect for the new Tom Bostic USC-UMP conversions. This section is the perfect length in order to do the USC/UMP conversion. Just in only...HKP-19798$0.00 -
Out Of Stock
H&K HK416, MR556 Ejection Port Cover - FDE
H&K Heckler & Koch
$0.00HK German HK 416, MR556 Ejection Port Cover In RAL7008 -FDE HK manufactured newer polymer style cover assembly found on the latest HK 416 & MR556's. This item can also be used on other AR15 style projects to enhance the project with the finest...HKP-19450$0.00