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 UMP Demilled Extended Rear Receiver Section - HKP-19798 HK UMP Demilled Extended Rear Receiver Section
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    HK UMP Demilled Extended Rear Receiver Section

    H&K Heckler & Koch

    $999.95
    HK German Factory UMP  Receiver Section - Extended Demilled factory HK UMP rear receiver section perfect for a USC-UMP conversion. With the folding stock attachment point intact right in front of the ejection port, this extended receiver section is...
    HKP-19798
    $999.95
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    $999.95
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  • HK MP5, MP5K, MKE AP5, AP5-P Case Deflector - 9mm Receivers HK MP5, MP5K, MKE AP5, AP5-P Case Deflector - 9mm Receivers
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    HK MP5, MP5K, MKE AP5, AP5-P Case Deflector - 9mm Receivers

    MKE

    $24.95
    MKE AP5, AP5-P, HK MP5, MP5K Case Deflector for 9mm Receivers This steel case deflector is manufactured by MKE for AP5 firearms and fits MP5-pattern 9mm receivers. It installs on the ejection-port flat of the receiver and is riveted or welded in place to...
    HKP-99349
    $24.95
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  • HK MR762 A4 Upper Receiver Kit - 16" HK MR762 A4 Upper Receiver Kit - 16"
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    HK MR762 A4 Upper Receiver Kit - 16"

    H&K Heckler & Koch

    $2,449.95
    HK UPPER RECEIVER KIT MR762 A4 - 16" The MR762 A4 upper 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...
    HKP-22424
    $2,449.95
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  • HK MR556, MR223 Upper Receiver - BLEMISHED HK MR556, MR223 Upper Receiver - BLEMISHED
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    HK MR556, MR223 Upper Receiver - BLEMISHED

    H&K Heckler & Koch

    $695.95
    HK MR556, MR223 Upper Receiver - BLEMISHED ONLY 1 UNIT AVAILABLE - AS PICTURED MISSING FORWARD ASSIST AND GAS PISTON COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE...
    HKP-16950-BL-B
    $695.95
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  • On Sale
    New - SIG Sauer / Phase 5 Hex Buffer Tube for AR-15 Pistols - BLEMISHED - HKP-99304 SIG Sauer / Phase 5 Hex Buffer Tube for AR-15 Pistols - BLEMISHED Sig Sauer / Phase 5 HKP-99304
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    AR15 Buffer Tube - Hex - 7.5" - BLEMISHED

    Sig Sauer

    Now: $19.95
    Was: $44.95
    SIG Sauer Phase 5 Hex Buffer Tube for AR-15 Pistols - BLEMISHED ONLY 1 UNIT AVAILABLE - AS PICTURED COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE FINAL. This buffer...
    HKP-99304
    Now: $19.95
    Was: $44.95
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    Now: $19.95
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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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  • New - H&K 21E/23E Left Receiver Reinforcement Rail Weldment - HKP-21907 HK21E, HK23E Left Receiver Reinforcement Rail Weldment
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    HK21E, HK23E Left Receiver Reinforcement Rail Weldment

    H&K Heckler & Koch

    $14.95
    H&K 21E/23E Left Receiver Reinforcement Rail Weldment Genuine German-made weldment for left-side receiver reinforcement rail. Precision-machined using the correct steel and milling for you HK21E or HK23E build. Compatible With: HK21E HK23E
    HKP-21907
    $14.95
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    $14.95
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  • New - HKP HK MP5 9mm Receiver Flat w/o Sling Clip - HKP-21828 HK MP5 Receiver Flat - 9mm - no Sling Clip
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    HK MP5 Receiver Flat - 9mm - no Sling Clip

    HKP HK Parts

    $189.95
    HKP HK MP5 9mm Receiver Flat w/o Sling Clip The MP5 9mm receiver flat serves as the foundation for custom MP5 builds. This version does not include a sling clip cutout, offering flexibility for customization. Precision-engineered for compatibility with...
    HKP-21828
    $189.95
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  • Out Of Stock
    Used - H&K 93/53/33 (5.56/.223) Rear Receiver Section - HKP-16481 HK33, HK53, HK93 Rear Receiver Section

    HK33, HK53, HK93 Rear Receiver Section

    H&K Heckler & Koch

    $79.95
    H&K 93/53/33 (5.56/.223) Rear Receiver Section Each rear receiver section is from a factory German HK 33/53 that was demilled and includes the welded on rear sight base and push pin bushing intact.
    HKP-16481
    $79.95
    Out Of Stock
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    $79.95
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  • HK MP5, HK94 Rivet for Case Deflector and Sling - Pack of 5 HK MP5, HK94 Rivet for Case Deflector and Sling - Pack of 5
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    HK MP5, HK94 Rivet for Case Deflector and Sling - Pack of 5

    LSC

    $3.95
    LSC HK MP5, HK94 Rivet for Sling Clip and Case Deflector - Pack of 5 Each case deflector, US or German-made, will require two rivets to attach the case deflector to the receiver or flat. You will need two of these for installing one case deflector...
    HKP-99400
    $3.95
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    $3.95
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  • On Sale
    HK UMP Paddle Mag Release - Extended - BLEMISHED HK UMP Paddle Mag Release - Extended - BLEMISHED
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    HK UMP Paddle Mag Release - Extended - BLEMISHED

    HKP HK Parts

    Now: $24.95
    Was: $34.95
    HK UMP Paddle Mag Release - Extended - 9mm / .40 S&W / .45 ACP - BLEMISHED COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE FINAL. Billeted alloy UMP magazine release...
    HKP-17919-B
    Now: $24.95
    Was: $34.95
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    Now: $24.95
    Was: $34.95
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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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