After doing some searches I am unsure about the differences in qev's. I cannot find any 1 inch qev's at all. I guess this all come with experience. So what would be the main advantages if I went qev over ball valve? How far do you think I would be able to launch objects at with this setup and at ...

Gun Freak, I actually was admiring your work last night and its wonderful that you've replied to my thread. That being said I meant compression chamber, thanks for correcting me :) The reason I want 2 end caps is because I would like to have the barrel mounted on top of the tank using 1 inch elbows ...

So for a few months I've been putting together a parts list on my pneumatic cannon that I will be building. Here are the specifications:

24" of 2" iron pipe (plan on getting it threaded) to make combustion chamber
2x 2" iron end caps (thread on)
1" ball valve
1" iron fittings (elbow joint etc ...