(this is the 3/4" threaded pipe in the diagram).
(that's a 5-pack in the link, so there are extras)
(and that's a 10 pack, so again, there are extras).
Not much to say here, the picture pretty much shows what I did. The barrel I used is 30" in length, with a 26" air chamber. Note it is important to let the PVC cement fully cure. A number of people have told me stories about how they eagerly tried their aircannons too soon, blowing out the air chambers. Pesco's first air cannon did not have the barrel glued into its connector, and consequently self destructed while firing for the 4th or 5th time!
In response to numerous requests from readers of this site, I've put together an online shopping list to help identify parts similar to those I used in my project:
(this is the 3/4" threaded pipe in the diagram).
(that's a 5-pack in the link, so there are extras)
(and that's a 10 pack, so again, there are extras).