
Reducing a 3/4" barrel to 1/4"
A 1/4 hole in a 2" piece of 3/4" dowel, a groove, an O ring, epoxy.
The 1/4" tube/piston goes into the 3/4" barrel.
A split dowel at the muzzle, a strong piece of Nylon reinforced hose and a pair of hose clamps, fixes the 1/4" barrel to the main chamber.
This technique could be used for almost any air cannon.
If I blow into the 1/4" tube, the 3/4" piston and 'arrow' is easily forced out of the 3/4" Type M tube. This movement indicates good seals and sliding smoothness.
BoyntonStu