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 G36, SL8 Paddle Magazine Release
USA
$17.95US Magazine Paddle Release for HK G36 and HK SL8 HK G36 Mag Release or mag catch. Compatible With: SL8 G36 G36K G36CHKP-18222$17.95 -
HK MP5K, SP89, SP5K Trunnion - 9mm - RS
RCM
$69.95MP5K Reverse Stretch Trunnion US-made to exact factory HK specifications for the HK MP5K, SP89 9mm builds. There is a difference between the MP5K and the MP5 trunnion. This offering is the correct trunnion for the MP5K and all MP5K PDW variants,...HKP-02242$69.95 -
HK417, MR762 Magazine Catch Spring
H&K Heckler & Koch
$9.95Heckler and Koch Magazine Catch Spring for HK417 and HK MR762 New HK German manufacture. Factory correct magazine catch for the magazine release. Compatible With: HK417, MR762 G28HKP-16520$9.95 -
HK21E, HK23E Rear Sight Base
HKP HK Parts
$38.95HKP HK Parts Rear Sight Base for HK21E, HK23E US manufactured billeted from solid ordnance grade bar stock. Each unit is precisely machined to factory tolerances. Requires post installation machining to accommodate a scope. Compatible...HKP-21467$38.95 -
HK G36, SL8 Cocking Handle Axle Pin
H&K Heckler & Koch
$11.95HK German G36 & SL8 Cocking Handle Axle Pin This is the rivet pin that is used to attach the swiveling cocking handle to the body of the carrier. These can be replaced as they break and wear. Compatible With: HK G36 HK SL8HKP-01877$11.95 -
HK MP5, MP5K Rear Sight Base - MIM and Machined
H&K Heckler & Koch
$14.95Heckler and Koch Rear Sight Base - Weldment for HK MP5 and HK MP5K New HK MP5, MP5K 17-4 Stainless H900 rear sight base. The most correct MP5, MP5K rear sight base available. The only factory correct sight base with the factory HK German side axis...HKP-19705$14.95 -
HK21, FMP21 Teardrop Rail Set - T-Rail
HKP HK Parts
$197.95HKP HK21/FMP21 Teardrop Rail Set HK teardrop style reinforcement rails. The ultimate choice for period correct builds. Expertly crafted in the USA from high-quality 4140 steel, these ready-to-weld rails are engineered for precision and durability...HKP-21671$197.95 -
HK MP5K Weldment Set, Complete
$59.95MP5K Complete Weldment Set Each set of weldments is all of the weldments required for an MP5K flat. Includes: Rear sight base Sight tab Case deflector Semi auto shelf Side reinforcement tabs 2 X rear stock bushingsHKP-16231$59.95 -
HK93 Trunnion
RCM
$65.00RCM HK93 Trunnion Made to exact factory HK specifications for the HK93, HK33 type builds. These are the best trunnions of their kind on the market. Machined to HK spec making the install painless and hassle free. The way a custom HK build it should...HKP-20807$65.00 -
HK MR556 A4 Charging Handle - Ambi
H&K Heckler & Koch
$199.95H&K HK MR556 A4 Ambi Charging Handle Upgrade your MR556 or HK416-style rifle with this factory H&K ambidextrous charging handle, designed for smooth, reliable operation from either side. Built to Heckler & Koch’s exacting standards,...HKP-21933$199.95 -
HK417, MR762 Buffer Tube Castle Nut
H&K Heckler & Koch
$44.95Heckler and Koch Castle Nut for Receiver Extension for Buffer Tube for HK417 and MR762 New HK German manufacture and the factory correct offering with the proper installation screws and staking guides. Compatible With: HK417, MR762HKP-16768$44.95 -
Out Of Stock
HK 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...HKP-17366$1,779.95