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.
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:
After grinding flat:
Marking off the dimensions and placement of the custom tab:
Scoring the boundaries with a cut-off wheel:
Space ground out:
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. 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:
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:
Final tab (I actually added some JB Weld to the "tip" to reinforce the wall in front of the hole):
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:
Original barrel nut ID:
All together except for the gas block. If you don't want or care about having a gas block, your all done now!
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.
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.
Slide the gas block on and tighten the set screw.
That's it folks! 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.
A close up of the upper:
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.