9mm SMG project + other HPA BBMG experimentation

[jackssmirkingrevenge]

General advice on purchasing, here it is in more detail

[BeNsKiii]

Is this automatic?, this looks very nice.

[Lockednloaded]

I just threw together one out of completely standard parts. It's not semi automatic Yet, but it works single shot and the detent is great. I think I can get semi auto if I just get a compression tee.

[the unit]

You don't think those brass fitting are at risk without the tank being supported elsewhere? For safety maybe you should have the tank also supported by the barrel, better safe than sorry especially with high pressure.

[jackssmirkingrevenge]

I just threw together one out of completely standard parts

... and it looks fantastic! Great job, is it 3/8" bore too? You should definitely add a tee mag

[Lockednloaded]

.4 ID barrel, .38 caliber slingshot ammo. I ordered a 1/4" male fitting X 1/2" compression X 1/2" compression. I'll probably use a sten style spring tube mag

Also you should know, it's not popping at as high of pressures as yours did, I think my BBs pop around 200 psi with my heat-shrink-tubing-detent

[Lockednloaded]

Upped the popping pressure with the addition of an actual o-ring seal. I could technically make it a .38 cal BBMG, but I couldnt afford the air or the ammo

[jackssmirkingrevenge]

Sexeh! Single shot then? We need some damage pics, I'll wager it can put a 3/8" breaing through quite a lot...

[Lockednloaded]

A little video, I could probably tighten up the detent, but it's a decent shot through a full can of pears



And some damage at three different popping pressures

[jackssmirkingrevenge]

It definitely sounds like it's not popping as high as it can, I'm not sure if it's the video not conveying it well but mine was pretty deafening.

[Lockednloaded]

Well mine has a longer barrel that ports into the sch80 sleeve, but also, I don't use continuous air to trigger the detent. I depress the pin valve on the tank just enough to barely let air flow. As I'm loading the pressure builds up to full. I then open the valve and a short burst of air is released so that I don't waste gas.

I doubt it is popping anywhere near 800psi, but as you can see, it went clear through that wood like it was cardboard, so I'm pleased with the results for now. The best part is that changing the power is as easy as a quarter turn of the compression fitting

[jackssmirkingrevenge]

Well mine has a longer barrel that ports into the sch80 sleeve, but also, I don't use continuous air to trigger the detent. I depress the pin valve on the tank just enough to barely let air flow. As I'm loading the pressure builds up to full. I then open the valve and a short burst of air is released so that I don't waste gas.

Still single shot though right?

The best part is that changing the power is as easy as a quarter turn of the compression fitting

Detents FTW A detent+interrupter prototype is imminent, just trying to figure out the best configuration which will be both reliable and easy to machine.

[Lockednloaded]

For the time being, I'd have a hard time shooting a semi-auto with this sort of power too often. I may add a mag at some point, but it's not one of my priorities at the moment. I really wanted a powerful, accurate, self-contained gun. I mean who doesn't?

Detents FTW A detent+interrupter prototype is imminent, just trying to figure out the best configuration which will be both reliable and easy to machine.

The old JSR would've been three prototypes deep already, has the machinery changed you?

[jackssmirkingrevenge]

For the time being, I'd have a hard time shooting a semi-auto with this sort of power too often.

Fair point, to be honest that's the reason I stopped developing mine further - at this sort of power levels 3/8" bearings quickly become "single use" and I haven't found a local source.

The old JSR would've been three prototypes deep already, has the machinery changed you?

True, it does change the way you think - since machining is more time consuming than slapping together some bits with epoxy and doing something else while it cures, there's a much bigger incentive for designing it well and "getting it right the first time".

[Brian the brain]

I depress the pin valve on the tank just enough to barely let air flow. As I'm loading the pressure builds up to full. I then open the valve and a short burst of air is released so that I don't waste gas.

So.. you understand why my pnuschnikov project never got finished.
Although air is free for me, I had to store it in a large CO2 fire extinguisher..and:

I really wanted a powerful, accurate, self-contained gun. I mean who doesn't?

Me too.So the extinguisher bit was a problem.

This, and the wasting of ammo on a large scale like JSR mentioned seem to be the real issues one runs into when building full auto or even semi cannons.

This makes the design part fun but then you are left with a cannon you're not really going to use.
Maybe just show it to a few friends and that's it.

So I get the single shot thing completely.
The launcher looks like a million bucks!
Have fun with it!