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Real-Steel Rainier Arms Raptor Charging Handle LM4 Compatible Modification Guide


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#1 Jeffsworkshop

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Posted 18 September 2013 - 03:35 AM

As promised, this guide will show you what causes the incompatibility of real-steel charging handles to the KWA LM4 GBB Rifle, and what steps were taken to overcome each problem.

Below are comparison shots between the RS Raptor Charging handle and the original that came with the LM4.
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Incompatibilities;
1. Dimensional
The RS charging handle is;
- Thicker along the whole stem
- Narrower along the whole width
- Shorter then the LM4 charging handle
- Slight raised "square" at the upper tip end
- Front tip that dips down further, which is designed to grab the Bolt Carrier during the charging motion
- Absence of two "channels" halfway along the upper left and right side of the charging handle, running from the middle to the tip. This design is intended to avoid the 2 "Hooks" half way through the insertion of the charging handle that act as anchors for the mid-section of the receiver rail, grabbing onto the the left and right side of the upper receiver pieces.
- Absence of a slight angled recess at the tip end of the charging handle.

The above covers the "Fitting" part of the puzzle. Now lets go into the "functional" part.
2. Functional
- As was mentioned above, where the real steel charging handle grabs the bolt carrier part during charging, the LM4 handle was designed to grab the fake gas key. The problem comes from the fact that where there is a solid flat surface on the LM4 charging handle for the fake gas key, there is a hole on the real steel that allows the gas tube passage to be inserted into the real gas key.
- Another issue that affect function is the shorter length to the RS handle. Where being shorter would not be an issue on the fitting of the handle into the LM4, there will not be enough material on the end of the RS handle to work with once modification is done to the dimension of the charging handle


The Solution;
Most issues in part one is easy enough to overcome, as it only requires the removal of material from the RS charging handle. The pictured handle was machined to the dimensions required to fit as outlined above.
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From the picture you can clearly see where material was machined away from the RS handle. Also note the slightly extended charging handle. We will go back to that later.

From the top;
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There is no visible alteration from the top side of the charging handle, at least when installed inside the LM4.

Now Lets tackle the upper receiver rail anchor...

There are two ways to go about doing this. First is to machine the two channels running along the upper side of the charging handle, just like what's present on the original LM4 handle. This way is preferred if you are not comfortable with the alternative solution below. The down side is that because the walls of the RS handle is thinner then the LM4 handle, taking out more material at the structural corners of the RS handle will further weaken the most stressful part, the hooking tip.

The second way is to simply remove the obstacle.
With any amount of range or field time with your LM4, that part of the rail is most likely loosened enough to be removed by hand. It is simply a piece of bent steel, fixed by two tiny pot metal welds onto the underside of the rail. If the front and back, thick solid attachment points that attaches the top rail to the side pieces not strong enough to hold your optics, this tiny hook will not likely be of much help.

Once the steel hook is removed, slight dremeling is needed to angle the hook attachment point;
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With earlier modifications, the RS charging handle should now be able to be inserted into the LM4!


With the fitments done, let's work on the actual charging of the bolt with the charging handle.

First we need to find a way to fill in the large hole on the RS handle, or some way to grab the gas key on the LM4. Also extending the RS handle to RM4's original length would give us much more material to work with, while strengthening the most stressed area on the charging handle.

What we did was to lathe a piece of aluminium rod to around 6mm diameter on one end, and hydraulic pressed into the RS charging handle. Excess material was milled off to the dimensions of the LM4 handle, together with the top angled recess. The inserted extension was pinned from the side, and any remaining gap between the extension and the handle tip was welded and milled off.
A coat of metal blackening paint was applied, and below is the result;
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From the picture you can clearly see where the extension was inserted into the charging handle.

Picture of the underside;
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The hole is now completely blocked, and very robust. There is only one problem: because the surface that interfaces with the LM4 gas key on the modified RS charging handle has slightly extended away from the muzzle, LM4's Gas key hits the handle tip before the bolt fully closes. There is only one way to remedy this issue:
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The very tip of the LM4 gas key was grinded off, filed and sanded to the current shorter length.

Alas, the modification of the Real Steel charging handle to fit into a KWA LM4 is complete. I doubt this is something people can get done one Sunday afternoon in their garage... But it is definitely possible if you have the will and the resources to attempt it.

Good luck!


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P.S. Special Thanks goes to KICbbgun.com.tw for their assistance in this project, and the unnamed Master Machinist/Welder located in the city of Taipei that made this project possible.

#2 BioRage

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Posted 18 September 2013 - 04:54 AM

Darn, no l"ike button"

+1 Like!

Thanks for the post, looks badass.

Edit:

Want to make a few more and sell them out? ;)

Edited by BioRage, 18 September 2013 - 04:55 AM.


#3 The Nutty Professor

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Posted 19 September 2013 - 08:36 AM

Looks fairly easy and can be done with a file if you take your time. I'm ordering one for my real steel and see what I got. Very nice write up.

#4 WTF?Shane

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Posted 20 September 2013 - 05:00 PM

Great write up.

#5 BeachEMT

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Posted 20 September 2013 - 09:32 PM

Very nice work Jeff. Just so everyone knows, I've been assured that the PTS Raptor charging handle will be out soon. Unless you really want to take on the project I would suggest you wait.

#6 Jeffsworkshop

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Posted 20 September 2013 - 10:31 PM

Thanks guys and I agree with BeachEMT, I'd wait for the PTS Version of this charging handle for the LM4 instead of attempting this mod.
I refreshed RedWolf Airsoft's pages for the LM4 version of the PTS Raptor Charging Handle every few days for 3 months, and could/would wait no longer, so I decided to do it myself.

The project took me around a month to complete, and almost $200 in cost. I also viewed it as a challenge as I read numerous posts where it was determined to be pretty much impossible,modifying a real steel charging handle to fit and function in the KWA LM4.

Edited by Jeffsworkshop, 20 September 2013 - 10:33 PM.


#7 BoobieM4H

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Posted 20 September 2013 - 10:59 PM

Nice work. I really appreciate seeing stuff like this.

GBBGURU






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