GM-94 Pump Action Grenade Launcher

[renegadecow]

I've been doing research on this project for nearly a year now and I've finally come to the point where I can actually start work after an epiphany from last nights 6-hour straight session of brain wrestling (brain won). Mechanically it is identical to the RMB-93 shotgun: a multi-shot, pump-action weapon with a reversed push-pull action and a tubular magazine on top... which amounts to nothing as not much is known about that shotgun and its internal mechanisms either. I had to study slow motion clips of the gun in action as well as high res images in different conditions of operation to understand how to replicate its inner function, most importantly the timing of ejection and reloading. The only thing I won't be replicating is a double action hammer as a simple plunger will suffice and the trigger actuated locking lugs to prevent blow over on the real gun. I'll be working with PVC for the most part and will likely make the folding stock out of aluminum due to very thin areas that plastic will definitely have some undesirable bendy qualities. It will use bog standard 40mm grenades instead of the proprietary 43mm because, well, there aren't any of those around. I'll be able to start drafting diagrams tomorrow. Like my China Lake from 2011, I'll only post pictures of large parts or entire assemblies revealing little detail as to how it functions specifically. This is to keep ARES from trying to steal my work and in having the tiniest glimmer of hope that some decent company might be interested in purchasing the designs later on.

 

edit:

I was supposed to start work on my GBB OTs-14 Groza w/ functioning GL, but I've taken quite a fancy to my WE AKS74U that I've decided to hold from butchering it. Plus it would make a great backup to this monstrosity.

[Skarclaw]

godspeed good sir

[Im going space]

revive the china lake project? but modernised.. heh.

i would very much like to see one working.

[DrAlexanderTobacco]

My body is ready.

 

Try to figure out how to put an EoTech on there like those spetznatz from Ukraine's riots

[renegadecow]

Sort of found out about that. Not sure if I want to anymore due to bulk of an offset mount. But a Docter or T1 sight right on the barrel would be sweet.

[PMO Gordo]

Bravo, sir! Would you consider changing the specs so that your GM-94 can load/unload longer rounds, such as the TAG shells and my G&P/P.M.O.G. projectile shells? The TAG shells are 125 mm in length, and the G&P/P.M.O.G shells are 133 mm in length. Also, the G&P shells are only 88 mm without the projectiles.

 

Also, I think this guy is also working on an Airsoft GM-94:

[renegadecow]

It will be length sensitive as far as shells go. Real 43mms are pretty long, at a guess right around 130mm. I'll be using the shells I have though which are 96-102mm. But studying the loading gate, it appears that having a gate made for a shorter shell will work with longer ones, but not vice versa.

 

Yeah, saw that project by Mr Dee (he made a China Lake too albeit very differently, and with rails). He's gone quite a ways now if you follow the link in the description. The problem is, and I don't want to tell him directly fearing I'd sound like a whiny tit, but I'm highly skeptical if his timing mechanism will work. Normally the catch holds the previously chambered grenade by spring tension until the pump is moved all the way forward causing the loading lever to push the spent shell out (overcoming said spring tension) and immediately locking the catch right after to keep the next grenade in line from falling to the ground. On his design it is reversed, the catch is locked when the pump is back which is redundant since the round will be chambered anyway. When his pump is moved forward, the lever will push the spent round and the next round along with it because the catch is left unlocked. Then there's the chamber load indicator that doesn't seem to work on his interpretation as it seems he mistook it as part of the loading mechanism.

 

See, I'm sounding like a tit already. I'll just leave this here and be on my merry way.

[Tinkerton]

Build two, and auction one off for charity. I know I'd bid!

[renegadecow]

If I built two, I'd keep them for dual wield and worry about how to reload them later.

[hwagan]

I was about to say 'But why would you need two pump action grenade launchers?' and then I re-read that sentence and realised how utterly ridiculous a question that is. 

 

Looking forward to seeing this one.

[DrAlexanderTobacco]

I was about to say 'But why would you need two pump action grenade launchers?' and then I re-read that sentence and realised how utterly ridiculous a question that is. 

 

Looking forward to seeing this one.

[Dr.Arnie]

Wow! I can't wait to see this develop, will you have it ready in time for my birthday?

[renegadecow]

Hmmm, when's that? I've got a crapload of automata to build and I was thinking of allotting a day a week for this project. Bit of a long haul until the end of the year as an ultimate deadline really (for ACBC 2014).

 

And here's the start of the diagram(s). As you all can see it's getting pretty crowded around the firing mechanism area and that's without drawing in the catch yet. I think I'll need to draw that and the loading lever separately, heads starting to hurt with all those lines intersecting.

Also, it's turning out pretty small actually. The grip just makes it look huge in contrast until you realize they're actually borrowed from a 9x18mm SMG.

[renegadecow]

Ok, was scratching my head for quite a while after drawing out the chamber load indicator and finding out that it doesn't actually reach the loaded round (causing the indicator to tip). A couple of videos after and it turns out to be a magazine load indicator. You pop open the lid, load a round and close the lid again. Indicator pops up. Charge the weapon and the indicator goes down until you put more rounds in the mag. The actual chamber indicator is simply the cutaway on the breech revealing part of the case's rim. I was right that the indicator isn't involved in loading shells from the mag, however it's what pushes the last round out not having any more rounds to push it down.

 

Also a bit of size comparison with the Lake. Despite having a barrel 2" longer and the same mag capacity, the 94 much more compact.

[Tinkerton]

Ok, i really really want one of these now.

 

PM me with a price, RC!

[viallet]

Always a fan.  Going to be watching this closely.

[renegadecow]

Some work done. Cut out the barrel, mag tube and receiver panels.

[suomipoika]

Always when I see your projects that plastic creeps me off.

[renegadecow]

Why? Were you traumatized by Cookie Monster as a child?

[Erka92]

Cookie monster, haha!

How much do you want for one of these? Do want!

Love your projects.

[suomipoika]

No its just that you use plastic instead of some kind metal but your creations are still great.

[renegadecow]

Believe you me, if I had the proper equipment I'd do it in steel. But plastic is as far as I can go with a jigsaw, drill and grinder.

 

@Erka92

Unfortunately shipping has and still is a problem for me. Maybe, just maybe I might be able to strike a deal with a decent manufacturer this time, maybe even smaller brands just so people can actually appreciate my work first hand for a change.

[Falcon_ASVV]

I hope so much you'll find a decent manufacturer for this one!

I want this Grenade Launcher so badly.

[Tw1tch]

This is sexy. Here's hoping you can entice someone who's not going to try and rip you off.

 

Out of curiosity what happened with ICS and the China Lake? Was it the fact  ARES had their eye and fingers on it so deemed it too risky?

[renegadecow]

They had asked what that mess was all about. I told them the honest truth, and don't know if it influenced it, but they just said they ended up being uninterested. Could be from failing to get substantial interest when they teased it on their Facebook page or they thought it would compete with their GLM sales not to mention incompatibility with then new TAG shells.