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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  • HK91, G3, HK93 Anti-Rattle Mag Release HK91, G3, HK93 Anti-Rattle Mag Release
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    HK91, G3, HK93 Anti-Rattle Mag Release

    MKE

    $32.95
    MKE Anti Rattle Paddle Magazine Release Upgrade your rifle with MKE's anti-rattle style paddle mag release. Compatible With: HK G3, HK91 HK33, HK53, HK93 HK PSG1, MSG90 In-spec clones and custom builds
    HKP-99348
    $32.95
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    $32.95
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  • On Sale
    Used - H&K MP5 40/10 Factory Trunnion - USED - HKP-99173 HK MP5 Trunnion 10mm / .40 S&W - Factory - USED
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    HK MP5 Trunnion 10mm / .40 S&W - Factory - USED

    H&K Heckler & Koch

    Now: $297.95
    Was: $549.95
    H&K MP5 40/10 Factory Trunnion - USED ONLY 1 UNIT AVAILABLE - AS PICTURED Used genuine German trunnion with round guides. Compatible With: HK MP5 40/10 THIS CLOSEOUT PART IS NOT ELIGIBLE FOR RETURN, REFUND, OR EXCHANGE.  SALE IS FINAL.
    HKP-99173
    Now: $297.95
    Was: $549.95
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    Now: $297.95
    Was: $549.95
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  • Out Of Stock
    New - HK UMP Paddle Mag Release Complete Assembly - HKP-19499 HK UMP Paddle Mag Release Complete Assembly

    HK UMP Paddle Mag Release Complete Assembly

    $19.95
    UMP Paddle Magazine Release - US Made - Assembly Complete New UMP Mag release. This is a very common repair & replacement part as they are fairly easy to break on the UMP lower. Simple & easy to install no gunsmith needed or required. Compatible...
    HKP-19499
    $19.95
    Out Of Stock
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    $19.95
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  • Out Of Stock
    New - HKP HK USC (.45 ACP) Carbine Mag Release - Extended - HKP-17918

    HK USC Magazine Release - Extended - .45 ACP

    HKP HK Parts

    $24.95
    HK USC Alloy Mag Release - Extended Billeted alloy USC magazine release. This is a very common repair & replacement part as they are fairly easy to break on the USC lower. With this new metal mag release you get more surface area as well as a much...
    HKP-17918
    $24.95
    Out Of Stock
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    $24.95
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  • Out Of Stock
    Used - H&K UMP (.40 S&W/.45 ACP/9mm) Demilled Rear Receiver Section - HKP-01659 HK UMP (.40 S&W/.45 ACP/9mm) Demilled Rear Receiver Section

    HK UMP (.40 S&W/.45 ACP/9mm) Demilled Rear Receiver Section

    H&K Heckler & Koch

    $0.00
    HK UMP Demilled Receiver Section This 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. Last one available.
    HKP-01659
    $0.00
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  • Out Of Stock
    New - HK UMP (.40 S&W/.45 ACP/9mm) Paddle Mag Release - HKP-18773

    HK UMP Paddle Magazine Release

    $9.95
    UMP Paddle Magazine Release - US Made New UMP Mag release. This is a very common repair & replacement part as they are fairly easy to break on the UMP lower. Simple & easy to install no gunsmith needed or required. Compatible With: UMP .45 UMP ...
    HKP-18773
    $9.95
    Out Of Stock
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    $9.95
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  • Out Of Stock
    New - MM HK 21 (7.62x51/.308) Trunnion - HKP-00246 MM HK 21 (7.62x51/.308) Trunnion

    MM HK 21 (7.62x51/.308) Trunnion

    H&K Heckler & Koch

    $0.00
    US Made HK21 Trunnion By Michael's Machine (MM) These are the finest US-made trunnions available.
    HKP-00246
    $0.00
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  • Out Of Stock
    Used - H&K 93/33/53 Paddle Magazine Release Set Complete-Used - HKP-00707

    HK33, HK53, HK93 Paddle Magazine Release Set Complete-Used

    H&K Heckler & Koch

    $0.00
    HK 93, HK33, & HK 53 Paddle magazine release set complete all pieces-Used
    HKP-00707
    $0.00
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