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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  • 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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    $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
    Was: $44.95
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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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  • 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
    Qty in Cart: 0
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    $79.95
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  • On Sale
    HK MR762 A4 Upper Receiver Kit - 13" - BLEMISHED HK MR762 A4 Upper Receiver Kit - 13" - BLEMISHED
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    HK MR762 A4 Upper Receiver Kit - 13" - BLEMISHED

    H&K Heckler & Koch

    Now: $2,199.95
    Was: $2,499.95
    HK MR762 A4 Upper Receiver Kit - 13" - BLEMISHED USED FOR TESTING - RAN 90 ROUNDS COSMETICALLY BLEMISHED PARTS ARE FULLY FUNCTIONAL AND SOLD AS IS. THIS PART IS NOT ELIGIBLE FOR RETURN. ALL BLEMISHED PART SALES ARE FINAL. The MR762 A4 kit contains a...
    HKP-22399-B
    Now: $2,199.95
    Was: $2,499.95
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    Now: $2,199.95
    Was: $2,499.95
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  • On Sale
    HK417, MR762 Upper Receiver and Handguard - Flecktarn HK417, MR762 Upper Receiver and Handguard - Flecktarn
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    HK417, MR762 Upper Receiver and Handguard - Flecktarn

    H&K Heckler & Koch

    Now: $1,340.95
    Was: $1,489.95
    HK417, MR762 Upper Receiver and 13.5" Handguard - Flecktarn Factory HK MR762 matching flecktarn upper receiver and 13.5" handguard.   ONLY 3 SETS AVAILABLE AND WILL NOT BE RESTOCKED Compatible With: HK MR762 HK417  
    HKP-99325
    Now: $1,340.95
    Was: $1,489.95
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    Now: $1,340.95
    Was: $1,489.95
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  • On Sale
    Used - H&K MP5 40/10 Factory Trunnion - USED - HKP-99173 HK MP5 Trunnion - .40 S&W, 10mm - Factory - USED
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    HK MP5 Trunnion - .40 S&W, 10mm - 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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    Qty in Cart: 0
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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 Magazine Release Assembly, Complete

    HK UMP Paddle Magazine Release Assembly, Complete

    USA

    $19.95
    UMP Paddle Magazine Release - US Made - Assembly Complete New UMP Mag release. This is a very common repair and replacement part as they are fairly easy to break on the UMP lower. Simple and easy to install no gunsmith needed or required. Compatible...
    HKP-19499
    $19.95
    Out Of Stock
    Qty in Cart: 0
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    $19.95
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  • Out Of Stock
    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...
    HKP-17877
    $699.95
    Out Of Stock
    Qty in Cart: 0
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    $699.95
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    Out Of Stock
  • Out Of Stock
    New - HKP HK USC (.45 ACP) Carbine Mag Release - Extended - HKP-17918

    HK USC Magazine Release - Extended

    HKP HK Parts

    $24.95
    HKP HK Parts Alloy Extended Magazine Release for HK USC Billeted alloy USC magazine release. This is a very common repair and replacement part as they are fairly easy to break on the USC lower. With this new metal mag release you get more surface area...
    HKP-17918
    $24.95
    Out Of Stock
    Qty in Cart: 0
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    $24.95
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    Out Of Stock
  • Out Of Stock
    Used - H&K UMP (.40 S&W/.45 ACP/9mm) Demilled Rear Receiver Section - HKP-01659 HK UMP Rear Receiver Section - Demilled

    HK UMP Rear Receiver Section - Demilled

    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
    Out Of Stock
    Qty in Cart: 0
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    $0.00
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  • Out Of Stock
    New - HK UMP .40 S&W, .45 ACP, 9 mm Paddle Mag Release - HKP-18773

    HK UMP Paddle Magazine Release

    USA

    $9.95
    US Made Paddle Magazine Release for HK UMP New UMP Mag release. This is a very common repair and replacement part as they are fairly easy to break on the UMP lower. Simple and easy to install no gunsmith needed or required. Compatible With: UMP Please...
    HKP-18773
    $9.95
    Out Of Stock
    Qty in Cart: 0
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    $9.95
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    Out Of Stock
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