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 & HK416 (5.56x45/.223) Upper Conversion Kit - Threaded 1/2x28 - HKP-17877 HK416, MR556 Upper Conversion Kit - Threaded 1/2x28, - 5.56x45 / .223

    HK416, MR556 Upper Conversion Kit - Threaded 1/2x28, - 5.56x45 / .223

    HKP HK Parts

    $699.95
    H&K MR556 & HK416 (5.56x45/.223) Upper Conversion Kit - Threaded 1/2x28 Finally an answer for all of those that have been wanting a 14.5" upper for an HK416 or MR556. This conversion kit adds an upper or a barrel option for your MR556, CR556...
    $699.95
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    New - HKP HK MR556/416 Upper 9" 416C Style Conversion Kit - HKP-18674 HK416, MR556 Upper 9" 416C Style Conversion Kit

    HK416, MR556 Upper 9" 416C Style Conversion Kit

    HKP HK Parts

    $899.95
    MR556 & HK416 Upper Conversion Kit - 9" - HK 416C Style Finally an answer for all of those that have been wanting as close to the original, rare unicorn of a find HK 416C 9" barrel conversion kit for 416 or MR556. Each conversion kit upper or barrel...
    $899.95
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    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.
    $0.00
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    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.
    $0.00
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    New - MM HK 23E (5.56/.223) Complete Feed Mechanism - HKP-17578

    HK23E Feed Mechanism - Complete - 5.56 / .223

    Michaels Machines

    $3,999.95
    MM HK 23E (5.56/.223) Complete Feed Mechanism New US manufactured HK23E feed mechanism complete with top plate and push pin. The complete unit a great spare to have on hand.  Compatible With: Factory HK23E and MM23E firearms
    $3,999.95
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