MP18 concept

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So, this is obviously an ambitious idea, but hear me out. An MP18 GBBR.

Now, in concept, a GBB is actually very simple. You provide it with a burst of a compressed gas, which travels into the bolt. The bolt is actually open at both ends, with gas sending the bb down the barrel on one end, and at the other end the gas pushes on the bolt carrier, sending it recoiling.

Additionally, like most simple SMGs (because it's one of the first lol) the MP18 fires from the open bolt. So all you really need for open bolt is a bolt, held open (eh?!) by a sear. Pull the trigger, dropping the sear, and the bolt slams forwards, picking up a round and firing it. This is further simplified by leaving the gun as a full-auto-only.


As you can see from this PPSh-41, the sear is simply a lump that holds the bolt back. Incredibly simple. (So simple that someone with malicious intent could possibly make one out of pipes and springs! It's a good thing terrorists buy their guns from Canadian Tire, like any law-abiding citizen!)

Now, originally, I wanted to use the WE "Trommelmagazin 08" for their Lugers. However, like most GBB airsoft guns, the magazines do not work when they're not upright, instead just sputtering and spewing ice. So that leads to my first inquiry! The WE P90 and the upcoming Northeast STEN GBB have magazines that are mounted "sideways."

(Here's the STEN.)
https://www.youtube.com/watch?v=zi32RJB2-nA

So what I'd like to ask is: Does anyone own one/know how this system works? And do you think it would be possible to splice such a mechanism into an existing magazine design?

Additionally, does anyone know how the bolt/valve kicker works on a true open bolt GBBR? I know that the WE Thompson exists, as well as the STEN above. I think that some of the Uzis/MACs on the market are also true open bolt?

Lastly, how does the bolt stop work on a GBB open bolt?

(Honestly, I feel like this project will be more viable once that STEN is on the market...)

[Styrak]

Lastly, how does the bolt stop work on a GBB open bolt?

Would keep firing until you release the trigger and the sear raised back into place and catches the bolt when it's at the back

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Originally Posted by Styrak

Would keep firing until you release the trigger and the sear raised back into place and catches the bolt when it's at the back

No no, I mean after the final round is fired. Since the bolt hits the gas valve as it goes forward, how does the mechanism "know" when to stop? In real steel it's easy, the bolt goes forward but there's no bullet to fire and send the bolt backwards, so it just stops. But with a GBB there can still be gas in the mag after bbs run out, so the bolt doesn't stop recoiling until there'd no gas left.

[Danke]

OK to start out the term open bolt used in airsoft usually refers to a WE system that works exactly like a normal firearm's closed bolt. When the last BB is fired a the mag follower trips the bolt catch and holds the breech open. The older system called Closed Bolt was more like a gas powered AEG.

Open bolt SMGs in airsoft are less common. Below is a video of a Tommy Gun. Since most SMGs don't have a catch they will continue to fire when the BBs are gone but there's gas in the mag. Some airsoft SMGs will have a catch built into the mag that's not 100% accurate to the real thing but will stop the dry firing.


https://www.youtube.com/watch?v=IbVknGQapgo

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Originally Posted by Danke

OK to start out the term open bolt used in airsoft usually refers to a WE system that works exactly like a normal firearm's closed bolt. When the last BB is fired a the mag follower trips the bolt catch and holds the breech open. The older system called Closed Bolt was more like a gas powered AEG.

Open bolt SMGs in airsoft are less common. Below is a video of a Tommy Gun. Since most SMGs don't have a catch they will continue to fire when the BBs are gone but there's gas in the mag. Some airsoft SMGs will have a catch built into the mag that's not 100% accurate to the real thing but will stop the dry firing.


https://www.youtube.com/watch?v=IbVknGQapgo

Yeah, I've seen some stuff like that, didn't some company release a "closed bolt" MP40 recently? I should have been clearer, but I meant open and closed bolt in terms of real steel. I'd assume maybe the follower itself could just stop the bolt? Or maybe instead of how other GBB mags have an arm that pushes the bolt catch up, an open bolt system could have a plate that pops up over the valve?

[Danke]

The follower spring usually has enough trouble tripping the catch never mind moving a hatch over the valve that would be heavy duty enough to resist the bolt hitting it.

I think something like this would have to become a hybrid gas/ptw/polarstar type of system that would count rounds and turn off the tap when the BBs were done.

From what I've seen if you want obscure models your best plan is to adjust your expectations to the AEG side of the room.