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
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 -
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 -
Out Of Stock
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 -
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: HK416 HK MR556 HK MR223 Looking for a matching lower for your build? STS416 A5 LOWER - Specialized Tactical...$1,559.95