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Beach's LM416 Upper Tutorial

LM416 HK416

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#1 BeachEMT

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Posted 28 August 2013 - 09:26 AM

Hey everybody,

I've had quite a few people asking me about how I made my LM416, so I figured I should finally post this up. The first method I will show (LM416 Mod 0, if you will), requires only some small power tools, a little know-how and a lot of patience. For those wondering, I do have access the a machine shop and I'm an award winning plastic/metal machinist. I decided to do this with tools that I thought most people had access to. For the dry stuff: By following this guide, you are doing this modification at your own risk. I take no responsibility or liablity for any damage or injury caused to any property or persons as a result of your modification or attempt thereof. Please follow all necessary safety precautions. Without further ado, let's begin.

Method 1:
1. Remove necessary parts from the JG 614. You will need: the barrel nut, barrel nut bolt and bracket/shims, rail system, upper receiver rail, and (optional) gas block.

2. Completely strip the LM4 upper and remove the top rail.

3. Carve out a space for the upper rail mounting tab. I used a Dremel cut off wheel the cut and grind the JG tab flat.

The JG tab before:
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After grinding flat:
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Marking off the dimensions and placement of the custom tab:
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Scoring the boundaries with a cut-off wheel:
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Space ground out:
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4. Make custom mounting tab. The dimensions were just taken from the KWA rail plus I added 6mm to the bottom. Additional height is necessary to allow it to be braced by the JG rail. I seemed to have lost my pictures of just the tab. :blinded: Basically it's an L shape with an angle cut on the back. (I need to look up my dimensions and I will post them asap)

5. Bond new tab to JG rail. I used JB Weld SteelStik (http://www.jbweld.co.../j-b-steelstik/) and just put a sh*t ton where I hogged out the material and stuck the tab in. Before the epoxy cured, I mounted the rail onto the receiver and cycled the charging handle a few times. We want the epoxy to fill in the most space it can for stability, but we want to make sure it doesn't interfere with any of the functions. This will also make sure the tab is perfectly aligned. After checking to make sure the epoxy wasn't bonded to the receiver or the charging handle, I actually let it cure mounted on the receiver with the charging handle locked.

Sorry it's grey-on-grey, but here's the tab bonded to the rail:
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6. Drill the hole for the roll pin. While the rail was mounted on the receiver, I carefully ran a 3/32" drill bit through the roll pin hole. Be very careful if you do this. You will seriously damage your receiver if you aren't lined up properly. If you aren't completely comfortable, I advise you to measure the hole placement and drill the tab by itself.

Rail mounted and lined up:
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Hole drilled:
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Final tab (I actually added some JB Weld to the "tip" to reinforce the wall in front of the hole):
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7. I used a carbide milling bit and a Dremel to shave out the ID of the barrel nut to 23.5mm (15/16").

KWA barrel OD:
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Original barrel nut ID:
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All together except for the gas block. If you don't want or care about having a gas block, your all done now! :clap:

8. Gas block installation: You need a full LM4 barrel or a just the base half with a 1" extension.

Fill in the pin grooves with epoxy. You wont use them and the front one interferes with the divot for the set screw.
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I lined up the center line on the gas block with the half way point on the old rear pin groove. This could be measured carefully, but I have a lot of experience. It's also only an aesthetic part so as long as it looks good. Like the upper rail, I just drilled through the gas block hole with a 1/8" bit.
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Slide the gas block on and tighten the set screw.

That's it folks! :thumbsup:  Pardon the long barrel and orange tip, I just used the OEM parts I had lying around. I'm currently looking for a good source of spray paint to make my upper AOR1/"gucci desert" colored.
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A close up of the upper:
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PS- For those who are curious, Mod 1 (WE/VFC parts) will be posted here as soon as it's done.

Edited by BeachEMT, 30 August 2013 - 05:51 PM.


#2 BeachEMT

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Posted 28 August 2013 - 09:34 AM

More coming soon...

Edited by BeachEMT, 13 March 2014 - 11:42 PM.


#3 proverbialguy739

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Posted 28 August 2013 - 09:37 AM

so am i to understand that the only changes are the receiver rail, the RIS system, and the gas block?

#4 BeachEMT

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Posted 28 August 2013 - 01:02 PM

Short answer: yes

#5 jet

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Posted 28 August 2013 - 04:22 PM

Nice! I right in the middle of this. Barrel nut is done. Having access to a lathe and boring bar is awesome.

I'm running into a issue with the JG upper receiver rail. I've shaved everything in the reciever(and then some) but when I push the rail foward the last  1/4" it hits on something in the receiver and the rail lifts up a couple of mm at the front of the reciever. I can push it down but I would rather it fit right.
Any thoughts about what the clearance issue is?

Kiiler write up. Can't wait to see the VFC, WE version.

Edited by jet, 28 August 2013 - 04:22 PM.


#6 BeachEMT

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Posted 28 August 2013 - 04:44 PM

I didn't even bother to fix that gap. I figured that given the quality of the parts I just had to resign myself to not having a perfect fit. There definitely is some fit issues between the the receiver "hook" and the rail's "shelf". You will notice my rail also sits a couple mm to the rear. Maybe try looking at that.

Your lucky you had the lathe for the barrel nut. It was a bitch to hog out that pot metal.

#7 jet

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Posted 28 August 2013 - 04:56 PM

It's really weird. Everything fits perfect until the last 1/4" inch. You can hear it hit something and then it lifts when you push the final 1/4".

I'll figure it out. That kind of stuff just bugs me. The RIS seems to be made out of decent metal. The barrel nut cut really easy with a boring bar.  The shop guy couldn't believe how soft it cut.

Hey stop teasing, how about a sneak peek parts list for the VFC/WE Mod 1 version :clap:

#8 BioRage

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Posted 29 August 2013 - 06:41 AM

Posted Image

#9 jet

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Posted 29 August 2013 - 06:02 PM

Fitment/gap issue solved. It has to do with the rear "hook plate" on the JG upper rail.
The little plate is about 1mm to low. You have to push down slightly on it to clear the receiver "hook".
It makes the front of the rail push up. Nothing to do with clearance issues at the front which I was banging my head about.

So here is the drill.

1. Shim the hook plate up about 1mm. The rail should slide forward and latch onto the upper receiver smoothly with no gaps.
2. Set in the front hook bracket in the Steelstik. ( Just use enough Steelstik to get it all lined up, you only have a 5 minute window to get it right, don't ask me how I learned this.)
3. Once the Steelstik sets, the rail and receiver should look aligned with no gaps. But the rear of the rail will wobble slightly. Don't sweat this
4. Add in a second batch of Steelstik to reinforce and bond in the bracket.
4. Take out the shim in the rear hook plate and gently snug down the two screws until the wobble goes away. I also used blue locktite as well.

Done! Perfect fit, no gaps at all.

Also I didn't want to fill in the front sight slots on my barrel.
Instead I threaded the pin holes in the JG front sight and used  8-32 x 1/8 Nylon Tipped steel hex set screws to hold the sight in place.
The nylon tips will not mar your barrel and you can always return it to stock.

All the mods are done, paint is drying and tomorrow is assembly day. I might post some pics as well.

Edited by jet, 29 August 2013 - 07:30 PM.


#10 BeachEMT

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Posted 29 August 2013 - 06:26 PM

Nice man! Glad we have another member in the club. :clap:  I had forgotten about shimming the rear shelf. I only did mine about .5mm which explains why I still have a small gap.

#11 BeachEMT

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Posted 30 August 2013 - 05:54 PM

I heard you guys enjoy a little tease ;)

Posted Image

Edited by BeachEMT, 30 August 2013 - 05:54 PM.


#12 jet

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Posted 30 August 2013 - 06:11 PM

Oooh nice. WE upper and VFC ris? Can't wait to see this put together.
FYI the VFC 416 buttstock won't work on the LM4 buffer tube. They must have made it like that so the RS guys couldn't use them.

Here is mine:
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You can see the nice fit of the upper rail and RIS rail. Rock solid all around.
Posted Image

Edited by jet, 30 August 2013 - 06:47 PM.


#13 BeachEMT

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Posted 30 August 2013 - 08:31 PM

It's all WE parts. I couldn't find a source for VFC parts at the time.

Very nice work on your upper jet. If I wasn't working on the other upper I would have spent more time on mine.

#14 jet

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Posted 31 August 2013 - 06:33 AM

Beach thank you for leading the charge on this. All credit to you for spec'ing this out.
I was shooting it at AEX yesterday and they were stoked about it too.

Really looking forward to your LM4/WE 416 MOD1.

Edited by jet, 31 August 2013 - 06:34 AM.


#15 BeachEMT

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Posted 31 August 2013 - 09:05 AM

Awesome! I'm glad people like it!

Just curious, did you use the stock LM4C barrel? It looks great and just about the right length.

#16 jet

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Posted 31 August 2013 - 01:35 PM

Yes. Stock LM4C barrel. Worked out great.

Now to figure out what to do with that JG 416 butt stock.

I actually like the cheek weld with this stock. Fits me better that my rs CTR go figure.
Too bad it looks so funky.

Have to see if I can make it look more like a real HK stock.

Or try to find a Marui one (good luck with that)

Edited by jet, 31 August 2013 - 01:40 PM.


#17 BeachEMT

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Posted 01 September 2013 - 10:10 AM

Any noticeable gap between the inside of the gas block and the barrel? The reason I was hesitant to use a LM4C barrel or a 1" extension with the LM4 base barrel, was the fact that the profile steps down right after the AR-15 block shelf.

If you are having problems with stock fitting, you could try using a G&P GBB buffer tube. Some modification is required but it will work (the threads need to be sanded down IIRC).

#18 The Nutty Professor

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Posted 01 September 2013 - 12:25 PM

Now hang on??? WE parts? I thought they were JG parts? Which WE? AAHHHHHH (Starts pulling what lil hair out he has) LOL

#19 jet

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Posted 01 September 2013 - 02:45 PM

In Beach's terms

416 Mod 0 is built with JG parts

The upcoming 416 Mod 1 is being built with WE parts

#20 jet

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Posted 01 September 2013 - 02:50 PM

Looking for some opinions here.

The JG crapalicious stock basically just exploded. LOL.

So after seriously thinking about getting a OEM HK 416E stock I've decided to go with the tried and true CTR.

So do I go all EBG (Evil Black Gun) or do the Coyote Tan furniture.

I'm getting the Tango Down foregrip, CTR stock and another BCM Gunfighter grip (If I go Tan).

Thoughts gentlemen. And lets keep it civil :innocent:





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