i have heard that before getting an empty co2 canister filled to stick the empty canister in the freezer for a few hours before getting it filled. supposedly you will be able to fill it up fuller. is there any truth to this rumor? seems to me if you get it overfilled you could have a nice explosion on your hands.
The canister are rated for a specific weight of product. They put that much in.
But, I do believe that they put a little in the tank. Then empty it. This action causes the tank to cool down so it takes a full fill better. At least that is what a paintball shop did with my little tanks.
http://www.ehow.com/how_2044754_fill-co ... -tank.html