3/4in QEV gun

[jim_himself]

At the moment, I am building my first QEV gun. My current setup is a 3/4in QEV with a 6in long 3/4 chamber and a 1/4in ball valve pilot. I hope to run it at 300psi+ once i get my shock pump. I still haven't decided on a barrel size. Any tips to make it more efficient or input on what barrel would be the best is appreciated

[BeaverRat]

I am almost positive that it will take decades to pump up that size chamber with a shock pump...

[jim_himself]

Im not so sure...it takes five pumps with a bike pump to get it to 120psi im guess it will ta ke about thirty pumps

[jackssmirkingrevenge]

I have to agree with BeaverRat, I find anything over 1 cubic inch becomes a bit of a chore with a shock pump, and you have almost 3 cubic inches there.

As to the barrel, calibre depends on what you want to shoot (BBs/marbles/anything in between) and in terms of power and efficiency, the longer the better (assuming barrel volume doesn't exceed volume of air in the chamber at atmospheric pressure)

[lozz08]

about ten minutes straight with your average shockie to fire one shot. Get a floor bike pump instead. Many will go 200 psi+ and take a minute to pump up that chamber.

[jim_himself]

Okay thanks for the input im probably gonna go with a .5in barell then i can use marbles and ball bearings

[Gun Freak]

Here is a high volume and high pressure pump that can push 300 psi.
And here is a smaller volume and cheaper pump that isn't a three stager but for your volume it would suit your needs.
As for barrel size, choose one in which the ammo can be of a constant size and that is cheap and plentiful. Airsoft bb's are a good example however I think you'd want to go with a larger calliber in this case.

[jim_himself]

I went with a half inch barrel, i used ball bearings i have from some magnetix kits i got a garage sale, i have about 1000 of them now. To fill it i use my friends air compressor and can get 200psi, performance is good, plenty of power but only so-so accuracy because of the smooth bore.

[Crna Legija]

Get a fridge compressor and you can get 500+psi with the flick of a switch, iv had myn too 800psi, someone took his passed 1000psi

[jim_himself]

Where can one obtain a fridge compressor. I dont have a spare fridge at the moment.

[Gun Freak]

Ahh yes I used those bearings before in a half inch barrel for this gun. They are a little loose but they work.

[Crna Legija]

Where can one obtain a fridge compressor. I dont have a spare fridge at the moment.

you don't, i always keep one in the corner just in case , try a junk yard or look around streets people always throw away old ones.

[jim_himself]

Well il start the hunt in my local junkyard.

[Crna Legija]

i got 3 from a junkyard just in case one didn't work and it only cost the entrance fee, i had to cut it out my self not hard but its illegal to release the freon in side them, something about the ozone