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This is the factory Heckler & Koch receiver extension nut, the part that threads onto your buffer tube and clamps it tight against the lower so nothing walks loose when you're shooting. It's the same castle nut HK uses on the MR556A1 and the 416 platform, machined from steel and finished in black. If you've ever stripped or rounded off a nut during a stock swap, you already know why starting with the real OEM piece matters.
The design carries HK's round tool attachment points along with traditional wrench flats. That dual setup means you can run the factory HK assembly wrench or reach for a standard castle nut wrench you probably already have on the bench. It threads onto HK factory buffer tubes and plays nice with both mil-spec and commercial diameter tubes, which makes it handy whether you're working on a genuine HK or a 416-style build.
A worn, damaged, or over-torqued castle nut is a quick way to end up with a wobbly stock or a buffer tube that backs out at the worst time. Dropping in the genuine HK nut gives you proper thread fit and the kind of clamping security the platform was engineered around. It's a smart one to keep in the spare parts box too, since it weighs nothing and you'll be glad it's there the day you need it.
Made in Germany to HK spec, this nut is cut for the 416 and MR556 family. Pair it with a quality buffer tube wrench and a torque wrench and installation is straightforward. It's a small part that does a big job, holding your whole rear assembly square and solid round after round.
This castle nut threads onto the end of the buffer tube and tightens against the receiver to lock the receiver extension in place. Once snugged down, it keeps the stock assembly from rotating or backing loose during shooting and handling. It's a key part of holding your rear assembly square and secure.
Yes, the HK factory castle nut is designed to work with both mil-spec and commercial diameter buffer tubes. It's cut for HK factory tubes on the 416 and MR556 platform but fits the common AR-pattern tube sizes as well.
It features HK round tool attachment points along with standard wrench flats, so you can use the factory HK assembly wrench or a common castle nut wrench. Pairing it with a torque wrench during install helps you set it correctly. Many builders also use a reaction rod or receiver block to hold the lower steady.
Yes, this is the factory OEM receiver extension nut made in Germany to HK specification. It's the same castle nut HK uses on the MR556A1 and 416 series rifles, which makes it the right choice for repairs, replacements, or a 416-style build.
| UPC | 642230249349 |
|---|---|
| Manufacturer | |
| Manufacturer Part Number | 50233165 |
| Color | Black |
| Model |
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