Do not fire your marker before every round!!! If your gun worked the last game why wouldnt it work the next(unless you dropped it)?!?! As for knowing how much air you have left, most Nitro tanks have a gauge on them. CO2 tanks can usually be judged on their size. I used to use a 20oz CO2 tank and I easily got 1000 shots out of it. Just remember, if your marker is properly maintained, and that it worked that last game it is more the likely going to shoot just fine for the next round. You should only be firing your marker in the chrono area, or one the field after that horn has blown to start the game.
