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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Out Of Stock
MR556 Upper Receiver Kit -16.5" - M-LOK
H&K Heckler & Koch
$1,779.95New HK Factory German MR556 Upper Kit with M-LOK forearm Includes: Complete MR556 upper receiver with M-LOK forearm MR556 Bolt group Complete Tungsten Filled HK Buffer HK Buffer Spring One 30 Round HK Steel Maritime Magazine No FFL required as the...$1,779.95 -
On Sale
HK MP5 Kit - Pistol Build - Flat, Top Rail, and Weldment Set - 9mm
HKP HK Parts
Now: $1,499.95Was: $1,899.95MP5 9mm Pistol Build Kit Complete German & USA Made Parts 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 pistol (N/A) rifle, or SBR...Now: $1,499.95Was: $1,899.95 -
Out Of Stock
HK MP5 to MP5SD Kit - Front End Conversion
DTAC Dakota Tactical
$1,299.95Dakota Tactical HK MP5SD Front End Kit If you have wanted to convert that MP5 or SP5 to an SD but didn't know where to start, look no further. Our kit provides all necessary components (aside from suppressor) to do so. With a DTAC Cage and SD guard...$1,299.95 -
HK 416A5 Stripped Upper Receiver - RAL8000
H&K Heckler & Koch
$1,559.95HK German Un-Assembled Stripped HK 416A5 Upper Receiver - RAL 8K Brand new factory German RAL 8000 416A5 upper receiver. Compatible With: HK MR556 HK MR223 HK 416 Looking for a matching lower for your build? STS416 A5 LOWER - Specialized Tactical...$1,559.95 -
On Sale
MR556 A4 Upper Receiver Kit - 16.5″ - 5.56 - M-LOK
H&K Heckler & Koch
Now: $1,795.95Was: $1,939.00H&K MR556 A4 16.5″ 5.56 M-LOK Upper Receiver Kit 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 system utilizes a piston...Now: $1,795.95Was: $1,939.00 -
On Sale
HK MP5 9mm Reverse Stretch Pistol Build Kit - Complete
HKP HK Parts
Now: $1,749.95Was: $2,099.95MP5 Reverse Stretch 9mm Pistol Build Kit Complete - German & USA Made Parts MP5-RS 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 pistol,...Now: $1,749.95Was: $2,099.95 -
On Sale
HK MP5 Kit - Pistol Build - Flat and Weldment Set - 9mm
H&K Heckler & Koch
Now: $1,669.95Was: $2,089.95H&K MP5 9mm Pistol Build Kit With Flat & Weldment Set Each MP5 9mm parts kit started life as an iconic German manufactured MP5 that was issued to the border guard and military police for service. During that service, they were carried a ton but...Now: $1,669.95Was: $2,089.95 -
Out Of Stock
HK416, MR556 Upper 8" 416C Style Conversion Kit
HKP HK Parts
$1,285.95Upper Conversion Kit for HK416 and MR556 8 inch barrel - 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 8" barrel conversion kit for 416 or MR556. Each conversion kit...$1,285.95 -
HK UMP Demilled Extended Rear Receiver Section
H&K Heckler & Koch
$999.95HK 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...$999.95 -
HK MR556 16" Complete Upper Barrel
H&K Heckler & Koch
$989.95HK MR556 16" Complete Upper Barrel Factory HK MR556 16" barrel, complete with a factory-installed barrel nut, gas block and flash hider. Every component is brand new and meticulously crafted, guaranteeing top-notch quality. This barrel is the ultimate...$989.95