I did something very similar, but used a butterfly valve rather than a sprinkler release. It meant needing to stand next to it and manually release, but it was

I did something very similar, but used a butterfly valve rather than a sprinkler release. It meant needing to stand next to it and manually release, but it was a lot cheaper. I also used 3/4" piping, which worked really well for lots of smaller projectiles, and meant that a female threaded adapter and some epoxy let me use 20oz or 2 liter bottles as tanks. I only got them to 80 psi, but I suspect they would have held just fine at 100. Soft projectiles would disintegrate in the air (no paintballing) but hard things- gobstoppers, batteries, frozen grapes- could cause a lot of fun destruction.