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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On Sale
HK MP5SD Kit - Pistol Build - 9mm
HKP HK Parts
Now: $2,249.95Was: $2,499.95HKP HK MP5SD Kit - Pistol Build - 9mm MP5SD 9mm parts kit complete with all the parts needed for an MP5 semi-auto pistol. Each kit comes with all 6 of the needed US made compliance parts. This is the first time that these iconic kits have been...Now: $2,249.95Was: $2,499.95 -
Out Of Stock
HK416 Upper Receiver Kit - 11.5" - 5.56
HKP HK Parts
$2,485.95HKP HK 416 11.5" 5.56 Complete Upper Kit Complete This top-tier assembly seamlessly fits onto your mil-spec lower or an STS 416 lower, providing the perfect solution for those seeking an 11.5" 416 style upper without breaking the bank. Each unit is...$2,485.95 -
HK MR556 A4 Upper Receiver Kit - 11"- M-LOK
H&K Heckler & Koch
$1,998.95H&K Heckler & Koch MR556 Upper Receiver Kit A4 -11″ - M-LOK This kit includes a complete upper receiver/barrel assembly, allowing Mil-Spec 5.56mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system. This...$1,998.95 -
Out Of Stock
HK416 Upper Receiver Kit - 10.4" - 5.56
HKP HK Parts
$2,485.95HKP 416 10.4" 5.56 Complete Upper Kit Complete Each kit includes the complete upper assembly, bolt group, tungsten buffer, & high-reliability SS recoil spring. This upper kit is a complete gas piston HK 416 style upper assembly that will drop on your...$2,485.95 -
On Sale
HK MP5SD Kit - Pistol Build - Flat, Top Rail, and Weldment Set - SEF Binary Trigger
Now: $1,999.95Was: $2,499.95HKP MP5SD 9mm Pistol Build Kit With Flat, Top Rail & Weldment Set - SEF Binary Trigger MP5SD 9mm parts kit complete with all the parts needed for an MP5 semi-auto pistol. Each kit comes with all 6 of the needed US made compliance parts to be legal as...Now: $1,999.95Was: $2,499.95 -
On Sale
HK MP5 Kit - Pistol Build - Flat, Top Rail and Weldment Set - 9mm - SEF Binary Trigger
Now: $1,859.95Was: $2,199.95MP5 9mm Pistol Build Kit Complete German & USA Made Parts- SEF Binary Trigger Group MP5 9mm parts kit complete with all the parts needed for an MP5 semi-auto pistol. Each kit comes with all 6 of the needed US made compliance parts to be legal as a...Now: $1,859.95Was: $2,199.95 -
HK MR762 A4 Upper Receiver Kit - 13"
H&K Heckler & Koch
$2,499.95HK UPPER RECEIVER KIT MR762 A4 - 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...$2,499.95