There isn't a whole lot of space between barrel and chamber, so for good performance you will need to take it to high pressures, 400 psi plus. I hope you can budget for a shock pump
Make sure you file and sand the end of the barrel where the piston seals to a fine finish and as close to a 90º angle to the length of the barrel as you can, otherwise the piston won't seal.
In order to keep the barrel centred when you glue it, this is a good technique:
Find a drill bit that is the same diameter as your barrel ID, and wrap the flat part of it with masking tape until the tape diameter is as thick as your chamber ID. Use this as a jig to keep the barrel centred as in the diagram until the epoxy cures.