SpudFiles

Guys well im starting my second mini coax since the first one sucked like hell! so my question is can i pilot off a 1/4 ball valve and have good performance or should i pilot off a shrader, if i do pilot off a shrader valve does it need to be very tight? the piston i am currently machining is a very tight fit, here some picture to let you see what i have so far.

That looks cool but will you concider using bbs instead of pellets because pellets tumble when they come out of a smoth bore right? What caliber are your pellets .177 or .22 ?. And is that sch 80 pvc?

You should be able to push the piston with your little finger and not much effort, as to the schrader valve it should be plenty to pilot something that small,as for the "tightness" i assume that you mean the tightness of the valve screw inside? If that is the case it should be tight enough so that it does not leak when pressurised but not so tight that you can't pump air though it.
Good luck with you project, what pressures were you planning on using?

I meant tight ness of the piston but well you've answered that haha but, these are .177 call pellets they have a hollow skirt in the back so they wont tumble much. Nova I was planning on using this at 160 psi since this sch 80 and the fittings will all be double layered and since the barrel is aluminum actualy,I obtained this barrel from a co2 pistol. And as for the piston I should glue on the sealing face instead of screaw cause i cant find a screaw small enough and if i did it would be hard to aline with the barrel without the screw in the way of the sealing

Pilot with a 1/4in ball valve you will get much higher performance.
A blowgun will work too but not not as well as a 1/4in ball valve.
About the tight piston just dremel it down a little and itll be fine.

Assuming you keep your pilot volume to the bare minimum, you should be fine with a schrader.

That looks cool but will you concider using bbs instead of pellets because pellets tumble when they come out of a smoth bore right?

Medium weight diablo-shaped pellets will fly straight without rifling.

I was planning on using this at 160 psi

Performance might be a little disappointing, these smaller coaxials need pressures of 300psi+ to really impress.

ah so i may invest in a shock pump then but im sure this body can handle higher pressures then 170+ right?

I wouldnt take it above 175psi because of the sch40 fitings if you replace those with sch80 ones id say 200psi-225psi.

ah, but i cant find sch 80 fittings in my area, oh well, but im buying a shock pump

Id recommened you make a high pressure pump but that is a lot of work and money.
You might want to remake the entire thing out of copper so you can go to 300+psi giving you a real use for that shock pump you are going to buy

im buying a shock pump and making a copper rifle, yes im calling it a rifle becuase it has a rifled barrel from a pellet gun 1/2 inch chamber so i can get high pressures

Sounds good almost exactly like my mini coaxial i have been mentioning in the world of spuds today thread.

hope your goes well and mine too

Your pipe looks a lot like the one I use in terms of colour and wall thickness, i know that doesn't say much about pressure rating but I've taken my pipe to 400 psi and beyond without ever having a single failure. The fact that it's only in short lengths and with high-strength epoxy endcaps helps too.

A high pressure pump costs about 20 -30 dollars to make and takes less than an hour to put together. The only thing that drives cost up is that you generally need to buy more copper pipe than you need.
The ones pictured on here are nice but generally have too much unnecessary extras added on.