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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  • Out Of Stock
    New - MM HK PSG1/21E/23E Forward Complete Assist Assembly - HKP-00852 MM HK PSG1/21E/23E Forward Complete Assist Assembly

    MM HK PSG1/21E/23E Forward Complete Assist Assembly

    Michaels Machines

    $779.95
    MM 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
    $779.95
    Out Of Stock
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    $779.95
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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 G36 (5.56/.223) Catch Axle - HKP-01872
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    HK G36 Catch Axle

    H&K Heckler & Koch

    $7.95
    HK G36 Catch Axle For All Lowers  
    HKP-01872
    $7.95
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  • New - H&K 91/93/33/53/G3 (5.56/.223) & (7.62x51/.308) Anti-Rattle Mag Release - HKP-01126 HK33, HK53, HK93, HK91, G3 Anti-Rattle Mag Release
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    HK33, HK53, HK93, HK91, G3 Anti-Rattle Mag Release

    H&K Heckler & Koch

    $64.95
    HK German Anti Rattle Paddle Magazine Release This item is a new H&K genuine part not used or surplus for installation on all HK .223 & .308 HK Rrifles. This is the highly desired anti-rattle-style paddle mag release. Compatible With: HK 91 HK...
    HKP-01126
    $64.95
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  • Out Of Stock
    New - H&K 93/53/33 (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 93,33,53 mag catch for magazine release.  Compatible With: HK93 HK33 HK53 HK33K Clone or other custom builds
    HKP-01059
    $49.95
    Out Of Stock
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  • HK MR762 A4 Upper Receiver Kit - 13" HK MR762 A4 Upper Receiver Kit - 13"
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    HK MR762 A4 Upper Receiver Kit - 13"

    H&K Heckler & Koch

    $2,499.95
    HK MR762 A4 Upper Receiver Kit - 13" The MR762 A4 kit contains a complete upper receiver and barrel assembly. The closed system design significantly reduces malfunctions typically associated with direct-impingement gas systems, as hot carbon fouling and...
    HKP-22399
    $2,499.95
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  • New - H&K CC9 Magazine Release & Chassis Pin - HKP-22112
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    HK CC9 Magazine Release & Chassis Pin

    H&K Heckler & Koch

    $5.95
    H&K CC9 Magazine Release & Chassis Pin   Made by H&K, this authentic pin for the CC9 secures magazine release and chassis components within the frame.   Compatible With: HK CC9  
    HKP-22112
    $5.95
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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 - .45 ACP

    H&K Heckler & Koch

    $18.95
    Heckler and Koch USC .45 ACP Magazine Release Axle 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 systems...
    HKP-02584
    $18.95
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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
    Out Of Stock
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    $275.00
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  • New - H&K HK MR762 Ejection Door Clamping Sleeve - HKP-16518
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    HK MR762 Ejection Door Clamping Sleeve

    H&K Heckler & Koch

    $4.95
    H&K HK MR762 Ejection Door Clamping Sleeve Compatible With: HK MR762
    HKP-16518
    $4.95
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  • HK UMP Paddle Magazine Release - Extended HK UMP Paddle Magazine Release - Extended
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    HK UMP Paddle Magazine Release - Extended

    HKP HK Parts

    $34.95
    UMP Paddle Magazine Release - Extended Billeted alloy UMP magazine release. This is a very common repair & replacement part as they are fairly easy to break on the UMP lower. With this new metal mag release you get more surface area as well as a much...
    HKP-17919
    $34.95
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    $34.95
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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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    $199.95
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