Connecting PVC to Copper...
It is impossible (or at least very unsafe and impractical) to connect copper directly to PVC in a pneumatic unless it is using threaded fittings, cam-locks, etc.
So you want a copper barrel for your PVC cannon? There are a few options
First of all, you can get a copper male adapter (which is the same size as your chamber) and a bushing that reduces the chamber size to your wanted barrel size. Solder the bushing into the male adapter, and then solder the barrel onto the male adapter. Just connect it to the PVC by a female adapter.
Another option is to sleeve the copper barrel inside of a PVC pipe, and then solvent weld the PVC pipe to the reducer.
So you want a copper barrel for your PVC cannon? There are a few options
First of all, you can get a copper male adapter (which is the same size as your chamber) and a bushing that reduces the chamber size to your wanted barrel size. Solder the bushing into the male adapter, and then solder the barrel onto the male adapter. Just connect it to the PVC by a female adapter.
Another option is to sleeve the copper barrel inside of a PVC pipe, and then solvent weld the PVC pipe to the reducer.