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i have a 3/4inch qev and want to use a popoff to make it full auto. i have a 150psi compressor and would use like a 120psi popoff. the chamber is around 40 cubic inches.
my main question is how i should make the mag/loading thing
i was thinking since i using 1/2inch sdr13.5 for a barrel i would use a 3/4 tee and 3/4inch pipe for the tube mag. i would have a reducing bushing on the barrel side and glue the barrel to that. i would use something so that the paintballs dontjust roll out the barrel and roll back toward the valve.
do you think this will work? if not, any suggestions?
In a tee mag without a bolt, the ammunition in the magazine is forced upwards with considerable force, I don't think paintballs could survive that sort of abuse.
With such a low tank pressure to firing pressure ratio, and with paintballs requiring a fair load of air to accelerate, I am guessing you could probably get 1-5 shots full auto, before the pressure dropped too low...
Either you are going to need a chamber the size of alaska, a much lower triggering pressure, or a much higher tank pressure.
With your given setup, you can do this quick rough calculation.
(Tank Volume)/(Chamber Volume)/5
That will give you the very low side of how many shots you can expect, though I am not entirely sure how close it will be.
Popoffs don't let out all of the air from the chamber, so you will get some increased effeciency there, but then again there is all of the time that the popoff is open, while the inlet hose is dumping air, that is directly wasted.
Still, you are looking at a crazy huge chamber of very few shots.
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I actually started qev + popoff too and with 180psi it still is a short burst of prrrrrrr out of a 600cubic cL chamber to supply and
thats with an 1/8" qev! and a very small air chamber.
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For the QEV + Popoff setup you really need a supply of high pressure air. The low pressure supplied from a normal air compressor dose not really provide a high enough margin of pressure. You only have to have you're air tank drop 30psi before the system will stop working.
right now i am getting about 5 shots at full pressure before my tank drops bellow 125psi and that is only with my little 6gallon commpressor. i have anouther mobile tank that i thought i could pressureish to 150 for an extra 10 gallons of compressed air but the tank is only made for 125psi so i will lower my pop off psi.
my compressor setup would have my compressor and tank at 150psi with the reg set at 125 and a hose to my tank. and then a hose to my gun. my gun would then have a 90psi popoff.
about the mag. i was hoping that by using just plain 3/4inch pipe capped off that there would be enough blowby and a small enough area in the mag that the paintballls would not move too much. also i would probably incorperate a bumper of some sort into the very top of it (probably a short spring).
will this design fire one paintball at a time or will it be more likley to shot multible per qev cycle?
When you start lowering the pressures that much you will probably loose most of you're performance
If you go for a Tee style mag, add a spring to the top of the mag. Paintballs will always be difficult to load due to them being so delicate, and because they are so light they get disturbed easily in the mag
generally you should only get one round per shot. If you don't have a stop for the ammo in the barrel you may encounter double feeds. This will also depend of the dwell time of the open QEV
even with a ball valve 90psi is still plenty powerful for me right now.
when you say to ad a spring to the top of the mag do you mean have a spring that pushes the paintballs down or one that acts as a bumper?
and for one of my unanswered questions...
should the mag be made of 3/4inch sch 40 or the barrel material? i was thinking the 3/4 so that i would have increased blowby decreasing the amount of hopping around the paintballs would do otherwise.
also i was hoping for about 100rpm but with my big chamber it might be able to fire that fast. this would allow the paintballs to dropdown again into the barrel in theroy.
also is a 1/4inch popoff big enough to piolet the 3/4inch qev? if not i could get a different but the adjustable one is 1/4inch so i was hoping to use that one
Click the link in my sig. I am building a semi-auto paintball laucher with a 3/4 qev, but its on hold due to school...
I did a whole lot of brainstorming, but there are newer designs that could be incorporated.
UPDATED MARCH '08
field-legal paintball semi
For the mag I would use tube that snugly fits the paintballs, you want to minimise the dead space in the mag, not make more of it. I don't know the American pipe schedules and ratings so I can't recommend a specific type of pipe, someone else can recommend that i'm sure.
The spring I mentioned would be to apply a light pressure on the paintballs to help feed and stop them from bouncing into each other. You want a nice long soft spring.
100RPM should be very achievable. I have had sinkers gravity feed at
I don't think you will have a problem piloting a 3/4 QEV with a 1/4 popoff, just keep the pilot volume to a minimum
ok so i will use the barrell material (1/2inch pvc sdr 13.5) for the mag
i am thinking that i will have a mag that runs pallel to the barrel and around 18inches long.
for the spring i will have to make my own because of the length
and at 100rpm i am not worried about feeding, filling the chamber up to pressure is what i am worried about
as for dead space i would have minimal fittings in there.
first would be a bushing to go from the 3/4 to 1/4, then a tee, and then the air supply
Why not consider going for a lower operating pressure, say 60-80 psi? you should still get very decent performance and your air supply will last longer.
i would be getting a popoff that is fully adjustable from like 25 to 200psi so i will experiment with different pressures
also will a paintball be able to fit through a 1/2inch pvc elbow?
Most fittings like that have a bit of a restriction slightly smaller than the pipe so the paintballs may not quite fit. A bit of patience and some sand paper and a file you would be able shape the inside of the elbow and get them to fit.
ok thanks alot.
i just made my own spring for the mag. it is made out of some .03inch mig wire witch is realy springy.
it is about 21inches and i will be puting it in a 18inch long mag so that it has some force even on the last paintball.
the length shold give me a capasity of around 22 paintballs.
so far my design is a 3/4inch qev with a 80psi popoff, a teemag with the springloaded tubemag running pallel to the barrel, a stop in the barrel so that you can point down, and 22 paintball capasity
do you guys think my new design will work?
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