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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  • Used - H&K HK 416/MR556 Enhanced Buffer Tube-Commercial - HKP-15424 H&K HK 416/MR556 Enhanced Buffer Tube-Commercial H&K Heckler & Koch HKP-15424
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    HK416, MR556 Buffer Tube - Enhanced - Commercial

    H&K Heckler & Koch

    $249.95
    HK 416, MR556 OTB (over the beach) Buffer Tube, Receiver Extension - Commercial: Genuine HK German manufactured 416, MR556 new style latest generation marine environment & over the beach buffer tube. Each Commercial buffer tube has built in drainage...
    HKP-15424
    $249.95
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    $249.95
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  • New - HKP AR-15 Commercial Buffer Tube - HKP-02728
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    HK AR-15 Commercial Buffer Tube

    HKP HK Parts

    $24.95
    AR-15 Commercial Buffer Tube Compatible With: HK MR556 & 416 All AR-15 style platforms Features: Made From T7 7075 Aircraft grade aluminum Made in the USA 6 Position Each features a highly polished inside tube Black Mil-spec triple hard coat...
    HKP-02728
    $24.95
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    $24.95
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  • New - H&K HK Mark 23 Magazine Release - HKP-01772 HK Mark 23 Magazine Release
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    HK Mark 23 Magazine Release

    H&K Heckler & Koch

    $24.99
    HK Mark 23 Magazine Release  
    HKP-01772
    $24.99
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    $24.99
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  • New - HK G36/SL8 (5.56/.223) Cocking Handle Spring - HKP-18369 HK G36, SL8 Cocking Handle Spring - US
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    HK G36, SL8 Cocking Handle Spring - US

    $9.95
    G36 Cocking Handle Spring- US Made   Compatible With: G36 All variants SL8 All variants
    HKP-18369
    $9.95
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    $9.95
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  • New - H&K 416 Front Takedown Pin - HKP-21862 HK416, MR556 Takedown Pin - Front - A4 Style
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    HK416, MR556 Takedown Pin - Front - A4 Style

    H&K Heckler & Koch

    $26.95
    H&K HK416, MR556 A4 Front Takedown Pin  The HK416 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...
    HKP-21862
    $26.95
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  • Out Of Stock
    Used - KDG HK MR762, HK 417, HK G28 Ambidextrous Magazine Release - Black - HKP-19204 Used - KDG HK MR762, HK 417, HK G28 Ambidextrous Magazine Release - Black - HKP-19204

    HK417, MR762, G28 Magazine Release - Ambidextrous

    KDG Kinetic Development Group

    $169.95
    Magazine Release - Ambi - HK MR762, 417, G28 The HK 762 Ambi (Ambidextrous) Magazine Release. This is the first ambidextrous magazine release for the HK 417 variant rifles.  The mag release is a lever instead of a button; where the release has been...
    HKP-19204
    $169.95
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    $169.95
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  • New - HK 416, MR556 Roll Pin for Charging Handle - HKP - HKP-16536
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    HK416, MR556 Charging Handle Roll Pin

    $7.95
    HK 416, MR556 Roll Pin for Charging Handle - HKP This is the shorter one that is used on the inside of the charging handle. There are two of these pins used per charging handle.
    HKP-16536
    $7.95
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    $7.95
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  • Used - H&K MP5 Rear Receiver Section - HKP-02167
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    HK MP5 Rear Receiver Section

    H&K Heckler & Koch

    $14.95
    H&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
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    $14.95
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  • New - H&K HK G36, HK SL8 Magazine Paddle Release - HKP-02152 HK G36, SL8 Magazine Paddle Release
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    HK G36, SL8 Magazine Paddle Release

    H&K Heckler & Koch

    $19.95
    HK G36 & SL8 Magazine Paddle Release Compatible With: HK SL8 HK G36 HK G36K HK G36C
    HKP-02152
    $19.95
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    $19.95
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  • New - H&K HK G28 Buffer Tube - FDE - HKP-16762 HK417, MR762, G28 Buffer Tube - FDE
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    HK417, MR762, G28 Buffer Tube - FDE

    H&K Heckler & Koch

    $224.95
    HK G28 Buffer Tube / Receiver Extension- HK Tan (Ral 8000) 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. Compatible...
    HKP-16762
    $224.95
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    $224.95
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  • New - H&K G36/SL8 (5.56/.223) Cocking Handle Spring - HKP-01862
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    HK G36, SL8 Cocking Handle Spring

    H&K Heckler & Koch

    $10.95
    HK German G36 Cocking Handle Spring - All Variants Compatible With: G36 - all variants SL8 - all variants
    HKP-01862
    $10.95
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    $10.95
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  • New - HK G36 (5.56/.223) Cocking Handle Bushing - HKP-18368 HK G36 Cocking Handle Bushing - USA
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    HK G36 Cocking Handle Bushing - USA

    $5.95
    G36 Cocking Handle Bushing - US Made
    HKP-18368
    $5.95
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    $5.95
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