I need some help with the ldt 3.0 hk416

Hello guys, I bought a ldt 3.0 body kit and a 7" ldt meta handguard, but the barrel nut that come with it does not fit into the body kit. Do you guys know what type of barrel nut the ldt body kit use, and can I have some specification about it too, please? I have been searching for the nut everywhere but can’t seem to find it

This is the sijun one that I’ve already had. And it does not fit

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Doesn’t fit as in the thread doesn’t fit the receiver or the handguard doesn’t fit over the nut?

As far as I was aware the thread is standardized and handguards were supposed to come with a matching nut.

The thread doesn’t fit with the receiver. The handguard I bought didn’t come with a thread so I have to buy one and it turns out they don’t fit

Huh, can’t say I’ve ever seen or heard of the threads not fitting, naturally the nut interface will be different per handguard style but the thread should always match.

Sounds like something Well would do tho.

Maybe contact whoever you got the receiver from and ask why it doesn’t fit.

Have you tried other nuts on it to see what actually is the wrong part .

I tried but sijun hk416 nut and this nut that comes with ldt metal handguard. They all fit in the handguard, but none can fit with the ldt body kit. So I’m just asking for some picture reference of the original ldt 3.0 barrel nut and the specification

I think I got one of the original nylon bodied LDT HK nuts at home somewhere but not sure where and I’m at work ATM.

Was a thick nylon one, but I know it’s the same thread size as any other M4 receiver I’ve got, and I got a few.

Can you help me measure the specification of the thread? Thank you for your help in advance.

I’ll see if I can find it when I get home

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Ah trouble is a lot of those barrel nuts are proprietary.

What yours is exactly I am unsure, hopefully Dchapo can help out. They vary in thread pitch. Good luck.


Couldn’t find it in my usual parts tub, will have to have a look in the other tubs in the morning :expressionless:


Yeah, they fit well into the handguard. But to fit onto the receiver is another thing, sadly.

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Thank you for your effort

Eventually found it

I don’t have a means to measure the thread pitch, but it fits any of my M4s and this printed shell is the same.

I don’t know how you calculate thread but the distance between valleys is 1.1mm and the depth looks to be about 0.5mm to 0.75mm on the receiver.

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Can you measure the other end of the thread? The one that you fit onto the receiver?

I can’t get the verniers in there unfortunately, and I don’t have a thread gauge, it’s reasonably firm threading it on so it would be ever slightly larger than the male thread

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You sir, are a life saver. Thank you for going through so much trouble.


I only have one more question. How do you set the area of engagement for the ldt hk 3.0 gearbox, since you have to manually install the spring and spring guide into the gearbox?
I tried but the spring always ends up pushing the piston and the sector gear and making them misaligned.

The angle of engagement? To move the piston back you pad out the front of the piston rack, like a washer (or if you can find them there’s sorbo pads made for it) between the piston head and piston body to make the rack sit further back, if any of that made sense

So between here

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But how do you make the piston teeth, the sector gear stays in place while you are putting in the spring? Mine always push the gears out of place