SpudFiles

I've been itching to make a co2 powered full-auto gun for the longest time, but I've never been able to get a decent regulator for a good price, so I decided to push two designs together to make my ideal full automatic gun: JSR's detent design, and psycix's pop-off design.

Together, with a little bit of vogt pattern loading, I have designed a full auto gun to run on un-reggulated co2.



sorry I didn't draw the pressure washer, but you get the idea

I also may mount a second 250psi pop-off on the chamber, just in case

Sexy, I like!

SPG had proposed a similar magazine back on spudtech, this was my interpretation of it.

I also may mount a second 250psi pop-off on the chamber, just in case

A wise precaution.

My greatest fear on this setup is that when I push the pressure washer handle, the first shot will fire then the pop-off will remain open and not go DAKKA DAKKA

Does the valve need to be modded to work in that way though? You might need a spring in the pilot for resetting and an equalisation hole depending how it's configured since you're feeding from the chamber side.

I will do initial test with out a spring just to see if it works stock. If that fails a weak spring will be added

McMaster has a good assortment of detents, including some with threaded bodies and even ones with pull rings for manual release. Keep that in mind if you have difficulty making/finding a detent.

As for the pop-off+QEV achieving full auto... I can offer no help. The uncertainty of the whole idea (properly sized pilot volume, suitable spring, etc.) turned me off to it a long time ago. Don't forget about the world of possibilites you get with a microcontroller and solenoid!

How does Mcmasters have detents? Got a part #? As for the actual pop-off, it'll pilot a 3/8" QEV a d it's fully adjustable up to 200 psi

My greatest fear on this setup is that when I push the pressure washer handle, the first shot will fire then the pop-off will remain open and not go DAKKA DAKKA

Unless the flow is really, REALLY big, or your popoff is weird, this will not happen. It'll just build pressure until the popoff pops, pilot the valve, firing the gun, and when the pressure drops, the popoff closes.
Be sure to fill from the pilot side, and of course the popoff should be able to handle a way larger amount of flow than the filling valve supplies.

The only thing I have my doubts on is the vogt pattern. Sure, it worked in the past and it can work now, but it is a potentially unstable design. I think it is very sensitive on spring pressure, barrel/ammo diameter and possibly ammo mass and friction.
I imagine air to slip past the ammo on the right when it fires, building pressure behind the balls, when the first ball leaves the barrel, the barrel vents its pressure, and the balls on the right get fired over the detent due to the air pressure behind them.
On the other hand, I have bad experiences with tube magazines as well, ramming the ammo all the way up into the magazine each shot.
Boltless loading mechanisms just tend to give problems.

Psycix, I actually want to fill chamber side

also, I've reconsidered using the pressure washer, and here's my reason: When I pull the trigger, the valve goes pop-pop-pop consistently in a perfect world, but when I release the trigger, there is still compressed co2 in the chamber. This not only poses a problem for inconsistent trigger pull to firing timing, but it also poses a safety cause. potentially, the chamber could be charged to as high as 190psi. this may not pose a safety concern for HPA, but with CO2, a rise in heat could cause the valve to go off, firing a steel bearing at normal speed. I may be paranoid, but I don't want even the slightest chance for a misfire.

I conclusion, I'm switching to a 1/8" slide valve so the chamber is vented when the trigger is not pulled

I don't think a sleeve valve will handle that pressure, maybe some hydraulic control valve but that's still pretty expensive, there are some decent priced 3way valves here but it's only 300psi

inconsistent fill delay shouldn't be a major problem because your making a full auto so the time between each shot shouldn't be very long, I'd just throw in a ball valve to bleed the tank manually

also I agree with psycix you should fill from the pilot

I have a slide valve rated for unregulated co2, I'll be alright on that front. My only problem with filling pilot side is that my pop-off will have to have much greater flow than my input valve, it would not allow me to use my slide valve, so I would be out another 20$ buying a pressure washer handle. Also, It wastes a lot of air when cycling full auto

the popoff valve should have enough flow, they're made to relieve pressure even if the input is running

well I understand where your getting it, it bothers me a little too and I hope there will be better alternatives in the future, but I don't think it'll work with a standard qev

Brian the brain has successfully modified stock QEVs to fill chamber side with a small EQ hole in the diaphragm and a weak spring, so the chamber side fill shouldn't the problem, but the detent...well thats a whole project in itself

Most popoff's dump air so fast the input flow is not significant.
Remember it dumps to atmosphere while your filling valve puts out air into a pressurized environment!

I'd recommend to fill from the pilot side. It will help quickly closing the piston as soon as the popoff closes, saving air.