OK...the tank is glued together.  You've got to love polyurethane glue. At the moment it lacks a release mechanism AND a way to pressurize it.  HOWEVER, I have tested it by using one of the water rocket launch heads to inflate it.  Then as a trigger all I have to do is pull out the launcher head.  I've only tested it at 20psi since I'm not 100% sure of the glue yet.  I'll try to get it up to about 100 PSI so I can be sure it won't break when I'm using it at 60ish.  Tests at 20 psi were just enough to throw projectiles about as far as I can.  Keep in mind, this is just barely enough air to displace all the air in the barrel...not much force.  At 40psi or more it will be FAR more powerful.  Another "unfinished" bit is...the barrel.  I haven't glued it in...just in case I want to test it with a longer barrel.  Hopefully that won't cause any...issues.