Not a lot. I used the blow dryer for a couple of minutes, then pounded the barrel out from the back. I'm hoping to finish this gun soon, maybe real soon because it's spring break, but the tools I need I have to borrow, so that could easily slow me down.

Thank you Jrrdw! The blow dryer worked extremely well. Props to you and Thunderlord. I didn't think that pvc expanded that much, but apparently it does!

@ iknowmy3tables: Actually, it wasn't unsafe, because I was careful to make sure nobody was standing where the bushing could come out and wasn't using high pressure, just enough to test the piston- the whole testing idea worked actually with no problems, no injuries, I just can't get it out because ...

Umm... It's pvc, not metal. Does pvc really expand enough? Thanks for the help, though.

I built a co-axial piston gun with a 3" chamber and a 1.5" barrel. This gun is like my avatar. The barrel goes through a modified 3"-1.5" bushing, that fits into a coupler on the chamber. I wanted to test the gun to make sure everything was working before I glued it all together so I wouldn't have t...

I'm learning French. Quite confusing, but it's ok. I'm in my fourth year.

The force of gravity causes things in free-fall to accelerate. The longer something is falling for, the faster it falls. In a friction free world, one can find the fall time using this equation: D=VoT+.5at^2 Where D= displacement, Vo= initial velocity, T= time, a= acceleration, If you plug the numbe...

The government applies silencer laws to any silencer that can be put onto a firearm.

I've heard that 4" is just a little small for the normal rolls of tp. I would suggest unwrapping a little off of the roll before the job... Also the double rolls aren't even close to being able to fit in 4".

That's because reducer bushings are socket x spigot. Spigot means that it fits into a coupler, not normal pipe.

SpudStuff is right. If I were you, I would cut those out now and replace them with couplers and reducing bushings.

If you want to protect your chamber from getting dinged up when paintballing, I would suggest you just wrap it in foam that will absorb the shock.

You have probably been putting too much fuel in. Try less fuel.

If I were you, I would use a stun gun. The bbq sparker won't have too big of a spark under pressure (I think). You might as well pay a few dollars more and get a stun gun for a much more reliable ignition.

I.Am.Awesome, abs, as long as it isn't cellular core is fine for use in combustion guns. Just don't use it in pnematics.