SpudFiles

i want to build a coaxal gun but i was wondering do you need to do anything to the back of the barrel to make sure it seals against the piston

No the piston is the part that does the sealing... just make sure your barrel is cut really straight... use the factory cut edge. also its not a bad idea to sand it a bit so its more like this on the lip ) rather then the normal ]

The rubber is on the piston, which is why you don't need it on the barrel.

Well just a few words of advise....

1. make sure your piston is perfectly round and fits in the chamber perfectly.

2. use a piece of rubber on the sealing face

3. make sure you line up the barrel in the chamber correctly.

The rubber is on the piston, which is why you dont need it on the barrel.

could you pilot it with a blow gun, im planning to have a 1.5 inch chamber

meh, you could....i would go with a ball valve or a sprinkler. both will give you way better preformance

ok, also want a thinner aluminum or brass barrel to save space, would jb weld work to bond that to the chamber at the frount

i would not do that(personally i might, but to be safe, no.)

if the ID of the barrel is that same on both, then whats the point (other than weight) i would just use the proper pipe.

copper pipe ok, but what about the jb weld is that stong enough

well, the jb weld would be stron enough, but would it have anything to grip?

why dont you get a coupler and go from (insert metal here) to (insert metal here)

i got ya
thanks