I'll cut to the chase, if you or a friend still use sprinkler valves show them this, I'll try to get a video to prove it if necessary. I built these two cannons with a friend who wanted to make an air Cannon. The small one was made for ping pong balls but my friend really wanted to try shooting tenn...

Glad you got a garage to keep it in, thermal cycling of the seasons wrecked a some of the more complicated PVC cannons I stored in sheds

The link is lost but I presume you're talking about the spyra water gun with that big Kickstarter campaign. I would look at a water pump like this 12volt RV water pump with a built in 80psi cut off https://www.amazon.com/dp/B074MZYS37/ref=cm_sw_r_apan_glt_fabc_MK5936AWFRVX9PYWN9DA?_encoding=UTF8&psc...

Sounds like an interesting idea, I think an adjustable chamber to barrel spacer would be great.

Also clamp on ergonomic grips for blowguns and control values

That's an interesting use of an air cylinder, but you really have the same effect from a QEV or a more common homemade piston valve. And as long as the air cylinder internal diameter is greater than the barrel diameter it should work fine. But I don't really see an advantage to using an air cylinder...

Thanks for the suggestions folks I ended up buying a section of metric PVC here MECCANIXITY PVC Rigid Round Pipe 45.2mm ID 50mm OD 350mm Light Grey High Impact for Water Pipe,Crafts,Cable Sleeve https://www.amazon.com/dp/B09J14XH93/ref=cm_sw_r_apan_glt_fabc_6N8GEHY78V6YNQNN7PKY?_encoding=UTF8&psc=1 ...

good news while it was fun to refresh my trigonometry and kinematic equations I found a projectile calculator online as soon as you enter an initial height time in flight and angle you should get a result https://www.omnicalculator.com/physics/projectile-motion based on your 16seconds at 45 degrees ...

Lol, I see what you're saying a lot more energy in the larger one used inefficiently. I'll make a video next time I visit my friend. Not a strictly controlled test but the large cannon was filled to something like 80psi the small cannon filled to a fraction of that shooting the same tennis ball we s...

I stopped by my friend's place made a simple test shooting shuttlecocks made from bottles at 60psi vertically