SpudFiles

im making a 15mm barrel sealing piston gun, with an 8mm (O.D 10mm)aluminium barrel.

i just have one question. How am i going to get the barrel to seal? Im not talking about the sealing face of the piston, im talking about in the end cap. you cant get fittingsd to go down to 10mm.

i was thinking of drilling a hole in a 15mm endcap, and then using some kind of epoxy to go around it.

the pilot will be a 1/4" blowgun, which i think will be sufficient. the piston will be hot glue, and the sealing face will be a rubber washer i bought for my other piston gun which failed. the working pressure will be about 30 or 40 psi, this will kind of be a gun thats just for fun to shoot around the house. just lobbing bbs or mini potato chunks everywhere.

You need surface area for the glue to stick, so here is my suggestion. Make 2 pvc washers to go around barrel and inside the 15mm pipe. Then, epoxy the first one into the pipe and onto the barrel, but make is like 15-20mm below where the 2nd washer will go, but don't put the 2nd washer in yet. Then fill the 15-20mm of space up with epoxy, then place the 2nd washer over it. This will give 15-20mm of epoxy gripping the pipes, this should be sufficient strength.