[lurkingknight]

bumping a year old thread?

Anyway, to somewhat debunk your advice while not entirely wrong, it's not entirely accurate (or complete)...

There's truth in properly matching air volume of your cylinder to your barrel in a ratio, while it may not have an effect on fps with one BB weight, overvoluming like you are suggesting creates higher than expected muzzle energy when using higher weight BBs on the same setup. In perfect lab conditions, you would expect muzzle energy of a .2 with X spring to be the same as a .3 with the same spring, minus the difference in velocity. When you fuck with the cylinder to barrel air ratio, the projected outcome starts to change. Overvoluming can net you higher velocity and muzzle energy with higher weight ammo. It's called Joule creep or energy creep. It's a common effect on GBB guns.

Yes you can use a non ported cylinder on a super short barrel. A ported cylinder will not necessarily give you less fps unless you drop below the magic ratio of cylinder volume to barrel volume to the point that you are undervoluming.