Receivers / Flats / Uppers

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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    New - H&K MR556 A4 11″ 5.56 M-LOK Upper Receiver Kit - HKP-21910 HK MR556 A4 Upper Receiver Kit - 11"- M-LOK

    HK MR556 A4 Upper Receiver Kit - 11"- M-LOK

    H&K Heckler & Koch

    Now: $1,799.06
    Was: $1,998.95
    H&K Heckler & Koch MR556 Upper Receiver Kit A4 -11″ - M-LOK  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...
    Now: $1,799.06
    Was: $1,998.95
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    New - H&K HK MR762/417 Castle Receiver Extension Nut For Buffer Tube - Black - HKP-16768 HK417, MR762 Castle Receiver Extension Nut for Buffer Tube
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    HK417, MR762 Castle Receiver Extension Nut for Buffer Tube

    H&K Heckler & Koch

    Now: $40.46
    Was: $44.95
    H&K HK MR762/417 Castle Receiver Extension Nut For Buffer Tube - Black New HK German manufacture and the factory correct offering with the proper installation screws and staking guides. Compatible With: HK MR762 HK 417
    Now: $40.46
    Was: $44.95
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    New - HKP HK 416 11.5" 5.56 Complete Upper Receiver Assembly - HKP-21539 HK416 Upper Receiver Kit - 11.5" - 5.56

    HK416 Upper Receiver Kit - 11.5" - 5.56

    HKP HK Parts

    Now: $1,988.76
    Was: $2,485.95
    HKP HK 416 11.5" 5.56 Complete Upper Kit Complete This top-tier assembly seamlessly fits onto your mil-spec lower or an STS 416 lower, providing the perfect solution for those seeking an 11.5" 416 style upper without breaking the bank. Each unit is...
    Now: $1,988.76
    Was: $2,485.95
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    New - HK G36 Backplate w/ Recoil Buffer - HKP-18538 HK G36 Backplate with Recoil Buffer - US

    HK G36 Backplate with Recoil Buffer - US

    USA

    Now: $40.46
    Was: $44.95
    HK 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...
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    New - HK G36/SL8 (5.56/.223) Cocking Handle Axle Pin - HKP-18367 HK G36, SL8 Pin - Axle - Cocking Handle - US
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    HK G36, SL8 Pin - Axle - Cocking Handle - US

    Now: $9.86
    Was: $10.95
    HK G36, SL8 Cocking Handle Axle Pin - US Made 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 models HK SL8 models
    Now: $9.86
    Was: $10.95
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  • Out Of Stock
    Used - H&K MP5, MP5K Case Deflector - HKP-00871 HK MP5, MP5K Case Deflector

    HK MP5, MP5K Case Deflector

    H&K Heckler & Koch

    $0.00
    HK German case deflector for receiver flat or receiver for all MP5, HK94, MP5K & SP89 builds. The case deflector is riveted or welded in place on the ejection port of the 9mm receiver/flat to aid in the extraction of the 9mm round. HK MP5, 94 HK...
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    New - HKP 416 10.4" 5.56 Complete Upper Receiver Assembly - HKP-17662 HK416 Upper Receiver Kit - 10.4" - 5.56

    HK416 Upper Receiver Kit - 10.4" - 5.56

    HKP HK Parts

    Now: $1,988.76
    Was: $2,485.95
    HKP 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...
    Now: $1,988.76
    Was: $2,485.95
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    New - H&K Cocking Tube End Cap Detent - HKP-18050
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    HK End Cap - Detent - Cocking Tube

    H&K Heckler & Koch

    Now: $4.46
    Was: $4.95
    HK German Cocking Tube End Cap/Dust Cap Detent HK German cocking tube detent for all steel and aluminum cocking tube end caps. Made of steel and finished in black.
    Now: $4.46
    Was: $4.95
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    New - H&K HK MR556/416 Roll Pin for Charging Handle - HKP-17063
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    HK 416, MR556 Roll Pin - Charging Handle

    H&K Heckler & Koch

    Now: $7.16
    Was: $7.95
    HK Clamping Sleeve or Roll Pin for Pawl On Charging Handle This is the longer one that is used on the outside of the charging handle. There are one of these pins used per charging handle.
    Now: $7.16
    Was: $7.95
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  • On Sale
    New - H&K HK G36/SL8 Complete Recoil Rod Assembly - HKP-01057
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    HK G36, SL8 Complete Recoil Rod Assembly

    H&K Heckler & Koch

    Now: $62.96
    Was: $69.95
    Recoil 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.
    Now: $62.96
    Was: $69.95
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  • On Sale
    Used - H&K HK MP5 Rear Receiver Section - HKP-02147
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    HK MP5 Lower Receiver - Section

    H&K Heckler & Koch

    Now: $49.46
    Was: $54.95
    HK 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.
    Now: $49.46
    Was: $54.95
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  • On Sale
    New - H&K HK G28 Buffer Tube - Black - HKP-16741 HK G28 Buffer Tube
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    HK G28 Buffer Tube

    H&K Heckler & Koch

    Now: $179.95
    Was: $199.95
    HK G28 Buffer Tube / Receiver Extension New HK German buffer tube with the proper slot cut for use with the G28 stock. This is the factory correct part needed to get the full range and use of the G28 adjustable stock. Made in Germany by HK.
    Now: $179.95
    Was: $199.95
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    Was: $199.95
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