"Nerf" M56 Smartgun from Lehui MG3

Mozzie

New Member
Project finally is far enough along that I am ready to post here.

After losing out on my Nerf M41A pulse rifle (moved to europe since the preorder and they are impos) and just can't track one down here, I decided to instead build a companion blaster from something a spotting on Aliexpress.

The base is the Lehui MG3 "nerf" gun. Which is a belt fed battery operated 75% scaled down MG3/MG42 dart gun.

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Despite the scale issue it's great that the whole blaster breaks down into modules, making it easy to work on and extend for my uses.

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Especially the stock, which will be important for extending the back of the receiver.

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The ammo drum is at a weird angle, I think so that you can hang the belt right over it (kinda like the old soup can trick on the M60 Machine gun to feed loose belts.

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It really ruins the profile though so cut the connector off, ran heat inserts into it and epoxied it back on.

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Next was the barrel, which I split in half and measured how much I needed to extend it by to get vaguely the correct length. I also removed the flash hider and front/rear sights. and cylinder for the anti aircraft sight.

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Taking measurements I designed a 3d printed insert to fit within the plastic and epoxied it on. Not pictured but I also printed an extension for the interior barrel. I thought about cutting all the holes out on the right side to be more accurate to the MG42 but it's all going to be covered by the forks and it adds mechanical strength to keep them.

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Then using the mesh from this M56 file on thingiverse I printed out the forks. I split them in half and used wooden skewer with holes in the mesh to align them. These forks now nicely cover my extension.

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After doing battle with the mesh geometry on that file I decided to freehand model all the rest of the printed parts directly in fusion using references and my own guesses. Once I've got this project finished I'm going to share the F3D file for anyone to build their own, Note though its a mix of all sorts of weird hardware/screws I had lying around with a lot of hand fitment after printing. So definitely adjust the CAD file for your needs

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First part I freehand modelled was the muzzle, which I am pretty happy about how it turned out. The 4 teeth are a bit fragile though, so print with extra walls so they are 100% full. (dont use 100% infill on models though, its a waist and adds internal stress to the parts, better to increase wall count so the polymer chains are aligned with the shape)

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Things were really coming together with the front, so now moved onto the receiver. Which meant opening it up. There was a screw hidden under the sideplates of the pistol grip, which are just friction fit so with a flathead you can pry them off. Inside you can see just how complicated the automatic system is, but it does show that the pistol grip itself can be cut off.

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I removed the bottom of the grip, and then designed and printed the rear receiver extension, it connects the same way as the buttstock did, but with two bolts running through it for extra strength. The rod is an 18mm curtain rod I had in a pile of junk. I also had an old coathanger that I'm using as the transfer bar for the trigger. Since the trigger doesn't have a good return force, I am going to put a spring on the rear brake handle so that it resets the trigger itself using the metal wire as a transfer bar.

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Don't have an in progress pic, but I did a flat black primer with a graphite powder rub which really came out great. I'm actually going to get some semi matte clearcoat to tone it down, but waiting for the gun to be fully assembled before I clearcoat it, so my handling continues to "wear" and weather the graphite coating.

I printed the trigger box to cover up the cut area. Had to do a lot of careful filling to not damage the wires for the motor that run in that area. I also increased the size of the bolts holding the extension as the original ones were flexing.

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Here is a video of the graphite treatment in motion.


I finished the tube for the transfer bar and the brake handle at the back. The handle itself has an extra spring I had from an old 3D printer extruder, that resets it instead of having the reset spring force on the original trigger, which just has a wimpy coil spring. It has a really nice feel, and cocking the gun in manual mode it has more than enough leverage to release the sear.

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Here is the current state of the project. I put a full paint treatment just to see if the receiver extension would blend in well. The muzzle is actually graphite rubbed over silver spray, for a different tone.

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Still to do is design and print the front grip assembly, the counter weight cylinder that hangs under the barrel, the top piece of the ammo drum. An extension for the cocking handle to be larger, plus 3 foam grips to attach (Which might need 3D printed inserts to increase the OD of the curtain rods) I am also thinking of hooking up the wiring to the foregrip, so there is a master "power" switch for the battery with an indicator light. I don't have plans or the money to spend on a knockoff steadicam vest yet, so leaving the clamp and bearings for a future project.

Now wish I could find an Nerf M41a as a perfect companion for it!
 
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Here is a review of that chinese blaster, which what I guess is an earlier revision with a previous paintjob.

When I ordered it from their website it took about 25 days to arrive in central europe.
 
Fantastic. I love how the graphite powder mimics a worn parkerized finish. I really enjoy seeing projects like this. It shows off a solid set of skills from both the old school and the new school of prop building. And I've recently found these chinese dart blasters too and have several on order to do builds with. One being the shell ejecting m249. Can't wait.
 
Fantastic. I love how the graphite powder mimics a worn parkerized finish.
First time I’ve tried graphite rub, I really like how to brings out the character of the surface material. I even left deliberate thumb prints so they look like oil etch stains.

Wish I could figure out what the bondo glazing putty equivalent is here (living in Poland for work). The difference in finish from the print lines and the smooth plastic is pretty extreme. I tried explaining what filler primer was through google translate at the home depot equivalent and it went nowhere :/

My goal for this project was not to exceed 120 euro all in, which I am pretty happy about so far. If I started again I’d consider an entirely 3D printed rear receiver and transplanting the mechanics, but that was way way beyond the scope of this project.

Also holding it I can definitely tell the ergonomics are based around having it on a vest and arm. Even the light plastic is a back destroyer.
 
You can always try printing with a lower layer height. It takes longer to print, but it saves you time sanding and filling. I've gone as low as .05 to get a smooth FDM print.

Filler primer has been difficult to get. I order my glazing spot putty from amazon as I can't find it locally at all. Tamiya makes it, bondo, and I think a few other companies have it on amazon.
 
Ordered grips and they sent the wrong type. I am going ahead with them for now just to get the project complete and then I can come back and tighten stuff up when I get the vest and steadicam arm part figured out.

I took the small charging handle and made a tube to go over it.

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I cut a slit so I could put the small trip into it

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A long 1/4-20 bolt then went into the top and through to clamp it together.

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I can definitely understand why its designed wit a smaller grip, the larger handle has more than enough leverage to rip it right out of the blaster. Definitely have to be careful with it.
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Also experimented with dry brushing, and then graphite powder rubbing over it.

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It blends the silver into the same tones as the graphite sheen, but has the harsh lines and slightly more reflective properties of the underlying silver.

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Example here where the graphite is the parkerized coating wearing away, and then sharper scratch lines and brighter where the steel is being damaged.

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Now need finishing touches of the barrel counterweight, which I am going to mount with the picatinny rail and then have to clearcoat and weather it.
 
Finally got the full blaster assembled and painted. Did very heavy drybrushing, especially against areas that would rub against the operator.

I did my silver paint drybrush, then graphite then clearcoated, which knocked it all down, then a final pass of silver drybrush on top for hard worn/chipped areas and then a final acrylic wash. Sometime next weekend going to record a video of it working. Plus share the fusion 360 file I designed it from
 

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Putting the foregrip puts a lot of torque on the barrel extension, broke the glue on one side..

The front half is reinforced by the struts, but the back is just the epoxy, so I've driven some M3 countersunk screws into it and painted the tops black.
 

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better picture of the final paintjob.

I want to run cables to the front grip that can connect and disconnect the battery. Though the fire selection mode is mechanical, with the manual cocking mode also functioning as a spring de-cocker, at least with the front switch I can have an indicator light or something to add to the "playability"

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Since I am moving onto electrical, here is the fusion / step file for printing the parts.
If you make any big changes or revisions, please share it on thingiverse as a remix.
 
I'm super stoked about this. I just ordered my MG3 and am planning on using/tipping you and your files off thingiverse. BTW - I dont recall if you said you were US or UK based, but Gamestop.com is where I bought my Nerf M41A recently.

As for the steadicam knockoff, now that I've found at least the mg base for this, I work IT in the medical field. We ordered these wall mounts for monitors that the staff didnt like so they all got ripped out. I took one home since they were going in the trash and plan on using it. Look on Amazon for Ergotron – LX Wall Mount System and that's what it is. Ergotron makes all kinds of higher end wall mounts. The tension on the arms is adjustable and my thinking is take one of the arms, but a chest mount into a harness then build the vest around it. I know it's not a steadicam but its as close as I will come. I've not done this. Just thinking it is the good armature around which to build something. If I do build it, I might end up welding but I'll try to keep in mind that fasteners may be all that folks have access to build something out.
 
BTW - I dont recall if you said you were US or UK based, but Gamestop.com is where I bought my Nerf M41A recently.
Even worse, I am now Poland based (moved for work, used to be in Canada) so the neef M41A is impossible to find on the continent now. Only scalpers on ebay.de now.

Using a monitor arm is an interesting solution, how fluid is their movement though? I imagine they would have dampers/frictoon on the rotating parts. Might be worth trying to drill out the holes and run flange bearings into the moving parts.

Also for a chest mount maybe a marching band snare/base drum harness would be a good starting point
 
I broke the charging handle on mine while moving recently, designed a replacement for it.
 

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