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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  • On Sale
    New - HK MP5K Trunnion - Gunsmith Special - HKP-99090 HK MP5K Trunnion - Gunsmith Special
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    HK MP5K Trunnion - Gunsmith Special

    USA

    Now: $24.95
    Was: $54.95
    HK MP5K Trunnion - Gunsmith Special US made HK MP5 trunnions sold as-is. Will require work before being functional. We recommend the work be performed by a professional gunsmith. The condition will vary from part-to-part vs. the pictured unit. Compatible...
    HKP-99090
    Now: $24.95
    Was: $54.95
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  • New - H&K HK MR762/417 Charging Handle Pin - HKP-16754
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    HK417, MR762 Charging Handle Pin

    H&K Heckler & Koch

    $6.95
    H&K HK MR762/417 Charging Handle Pin HK MR762 & HK 417 Clamping Sleeve for plate on charging handle. There are two of these pins used on the charging handle. Compatible With: HK MR762 HK 417
    HKP-16754
    $6.95
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  • New - H&K G36 (5.56/.223) Cocking Handle Bushing - HKP-01869
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    HK G36 Cocking Handle Bushing

    H&K Heckler & Koch

    $9.95
    HK German G36 Cocking Handle Bushing
    HKP-01869
    $9.95
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  • New - H&K USC (.45 ACP) Carbine Mag Release Axle - HKP-02584
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    HK USC Magazine Release Axle

    H&K Heckler & Koch

    $18.95
    Heckler and Koch .45 ACP Magazine Release Axle for HK USC Replacement magazine release axle for HK USC .45 ACP platforms. This component is commonly replaced due to wear or breakage and may also be required when configuring compliant magazine release...
    HKP-02584
    $18.95
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  • Out Of Stock
    New - HK33, HK53, HK93 (5.56/.223) Magazine Catch - Latest Design - HKP-01059

    HK33, HK53, HK93 Magazine Catch - Latest Design

    H&K Heckler & Koch

    $49.95
    Heckler and Koch German Factory Magazine Catch for HK33, HK53, HK93 New HK German HK33, HK53, and HK93 mag catch for magazine release.  Compatible With: HK33, HK53, HK93 HK33K Clone or other custom builds
    HKP-01059
    $49.95
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  • New - H&K HK MR762/417 Cylindrical Pin For Stop Pin - HKP-16619
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    HK417, MR762 Cylindrical Pin for Stop Pin

    H&K Heckler & Koch

    $9.95
    H&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 417
    HKP-16619
    $9.95
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  • New - HKP HK G36/SL8 (5.56/.223) Cocking Handle - HKP-18251 HK G36, SL8 Cocking Handle
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    HK G36, SL8 Cocking Handle

    HKP HK Parts

    $49.95
    Cocking Handle For G36 & SL8 Bolt Carriers - USA New USA made charging handle ideal for a 922 replacement part. Made in the USA.
    HKP-18251
    $49.95
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  • Out Of Stock
    New - MM HK 21 (7.62x51/.308) Factory Style T- Rail Set - HKP-00823 HK21 T-Rail Set - Factory Style

    HK21 T-Rail Set - Factory Style

    Michaels Machines

    $275.00
    Michael's Machines HK 21 (7.62x51/.308) Factory Style T-Rail Set HK21 US-made rails for all HK21 builds. This is similar to the rails above, only prepped/cut for the HK21 feed mechanism.  
    HKP-00823
    $275.00
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    $275.00
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  • On Sale
    New - HK MP5 Trunnion - Gunsmith Special - HKP-99089 HK MP5 Trunnion - Gunsmith Special
    Add to Cart

    HK MP5 Trunnion - Gunsmith Special

    USA

    Now: $24.95
    Was: $54.95
    HK MP5 Trunnion - Gunsmith Special US made HK MP5 trunnions sold as-is. Will require work before being functional. We recommend the work be performed by a professional gunsmith. The condition will vary from part-to-part vs. the pictured unit. Compatible...
    HKP-99089
    Now: $24.95
    Was: $54.95
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  • New - HKP MP5K 40/10 Receiver Flat - HKP-18033 HK MP5K Receiver Flat - .40 S&W, 10mm
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    HK MP5K Receiver Flat - .40 S&W, 10mm

    HKP HK Parts

    $199.95
    MP5K-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
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  • New - H&K HK MR556/416 Enhanced Buffer Tube - Tan - HKP-22086 HK416, MR556 Enhanced Buffer Tube - Tan
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    HK416, MR556 Enhanced Buffer Tube - Tan

    H&K Heckler & Koch

    $192.95
    Tan HK 416, MR556 OTB (over the beach) Buffer Tube, Receiver Extension - Commercial Genuine HK German-manufactured 416 & MR556 latest generation, marine environment & and over-the-beach buffer tube. Each commercial buffer tube features built-in...
    HKP-22086
    $192.95
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    $192.95
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  • Out Of Stock
    New - H&K HK G36, HK SL8 Roll Pin for Gas Piston - Black - HKP-16386

    HK G36, SL8 Roll Pin - Gas Piston

    H&K Heckler & Koch

    $9.95
    H&K HK G36, HK SL8 Roll Pin for Gas Piston
    HKP-16386
    $9.95
    Out Of Stock
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    $9.95
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