I’ve been thinking about a way to have a ‘proper’ functioning grenade launcher in my Pulse Rifle for a while. Considering all the various options available which others have explored always had compromises.

Spring shotgun is too few bbs being launched. Mini moscarts are hard to get and would seem to require some disassembly to reload. Gas shotguns usually have the stock as the air reservoir so can’t be cut down (and are expensive).

I got a small 40bb rail mounted gas powered launcher (sold as an HG 138) and managed to carefully modify it and the spas cage to get it functional.

It’s fired by racking the pump handle backwards. Reset involves using a small lever inserted through one of the holes in the spas cage. Gas refill is via a very small hole in the pump handle. The bbs are quick to load as I made a short ‘barrel’ for the launcher which you can just pour a bunch of bbs into and squish them into place.

The fitment is reversible should I wish to go back to the dummy shotgun arrangement apart from the small hole in the pump handle and another hole behind that in the side of the spas cage.

The modifications required fabricating aluminium parts to allow the launcher to mount to the underside of the barrel vent arrangement, a new aluminium ‘crossbar’ at the front and a 3D printed front cap with a wider barrel. A short aluminium barrel, and some modifications to the fake shotgun breech as well as careful modification of the spas cage itself.

The extra weight added (160g) has been offset by the change of the previously aluminium Front cap assembly to the 3D printed version, and changing the 1000mah nimh battery to 1600mah lipo . Total Added weight is 30g, or the weight of a fast food tomato sauce sachet

I have some specific parts on order which when fitted should allow both the firing and reset of the launcher to be carried out via the pump handle.

Brilliant solution!

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AKA: Simon

Have you looked into airsoft APS type shotgun shells? They operate on green gas appear to hold 12 bb's in a single large chamber. (Though, I've been wrong before... once or twice.)

Envisioning a urethane rubber or latex foam "bullet" shaped like the upper half of the M-40.

Yea I’ve seen those. The guns are 8 times more expensive than the little launcher I have, and while the action is very realistic it does mean after cycling the action you then need to scrabble around on the floor for your ejected shell, plus the cases and tops are consumables. Then there’s the added weight.

I think if you were going for a ‘replica’ approach where you needed the action to be true to the original prop, but still wanted it to fire pellets then that would be a good option.

I’ve been considering something similar to this, but with one of the holdout “launchers” that use a single gas shotgun shell.

The goal is to conver the front locking mechanism to go on the bottom, and load and unload the shell from the front.

As an update to this, I made it so the reloading uses the pump action in reverse (rather than a lever), and I also made a speed loader for the BBs to reload all 40 in less than a second (yes really!)

Check out the video link below to see it in action

https://www.youtube.com/watch?v=rtu_2st-SsI

It looks great and gives a functioning aspect to the otherwise redundant GL feature. Well done. My PR uses a Maruzen M870… the issue with that is that it has no gas reservoir. Which was originally in the stock of the M870. A custom made tank would be the way forward…

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A02/TQ2.0.52141E1

"Errr... Roger that's a 2-1-6..."

One of the UK members was/has/made custom gas reservoirs before... maybe worth putting up a WTB thread?

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Cpl Aron "septic" Williams
A10/TQ0.0.82146E1

Who was that? Was it SAS? Or DATA?

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A02/TQ2.0.52141E1

"Errr... Roger that's a 2-1-6..."

Wonder where they'd fit? Not alot of space once the GL section is used up, bearing in mind you have to relocate the battery too.

Well, I'll post some pics when I get home

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Cpl Aron "septic" Williams
A10/TQ0.0.82146E1

Have you done them, Septic?

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A02/TQ2.0.52141E1

"Errr... Roger that's a 2-1-6..."

Sorry nope, but I did buy a PR that's ex-UKCM years back. I *think* Simon might have done the gas tank mods, I'll ask around.

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Cpl Aron "septic" Williams
A10/TQ0.0.82146E1

It was Simon Smith who did an excellent job on the hero build on my PR… the challenge is space in the SPAS CAGE or locating another space for a gas tank that can be filled easily… it would need something to be made custom

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A02/TQ2.0.52141E1

"Errr... Roger that's a 2-1-6..."