Yeah - the dwv reducer was about all I could find that wouldn't have been 3-4 bushings to get down from 4" to 1".

The thing is pretty heavy. Especially with the golf ball barrel.
I may add a support at the end but it make changing the barrels a pain.

I built this as my first air cannon and I think it works great. I was shooting with the 2" potato barrel about 165+ yards. A golf ball probably about 300+ yards. This was only at 60 - 80 psi. The chamber is 4" x 30" pvc and the barrels are from the top: 1 1/2" SDR-26 sleeved in SCH-80 for golf balls...