SpudFiles

I know that pressurizing PVC and ABS pipe is dangerous, but what about for the barrel?

Since the barrel isn't sealed, it isn't necessarily being pressurized like the chamber. It's mainly used to direct the air flow.

I presume the amount of air pressure in the barrel would be relative to the weight and friction of the projectile. So if the projectile is not extremely tight or heavy then there shouldn't be much pressure building up in the barrel. Let me know your thoughts.

You also need to consider the pressures you're dealing with. 120psi, probably not a problem. 4000psi, not a chance. Another thing to keep in mind is what exactly you're shooting. I fired a paintball out of my first hybrid. It must have burst about halfway down the barrel, and the barrel (decently thick-walled aluminum paintball barrel) mushroomed around the circumference right in the middle.

Like pennywise said, depends.
I don't think anybody's actually measured it but using HGDT usually shows higher pressures in the barrel when modelling hybrids.

Here is a quick GGDT model of a pneumatic launcher with a 0.25 C:B ratio and a relatively lightweight 25 gram projectile in a 1 inch diameter barrel.

The model suggests that starting with 300 psi and using a fast valve, the pressure in the barrel spikes at 250 psi, the blue line on the graph indicates chamber pressure while the red line indicates barrel pressure.

That means that the barrel sees 80% of the chamber pressure as the projectile begins to accelerate.

Of course not all launchers are so efficient, but with faster valves and heavier projectiles it is something to keep in mind.

As someone who has pressurized ABS Cellcore enough to wring 800fps from a sprinkler valve, I'm not exactly Mr. Safety, but I do wonder what your reservoir/chamber is made of. Can you make your barrel from that?

If you just really like the smooth walls of the plastic pipe you can reinforce it by wrapping with fiberglass and epoxy. I've done this several times including wrapping copper with Kevlar to get a calculated burst strength of 20 000psi (special project). It is cheaper to source aluminum or steel tubing unless you already have the composites, but it is fun to try different things

nice gun is there any way i can help you improve it?