Actually the myth of freezing paintballs is BS The paintballs have a oil much like vegtable oil that wont freeze with out a dewar
all that happens in the shell gets far more brittle and the paint will break in the gun far more often
The guns obviously arent lethal but in a low light situation a paintball gun may look like a real gun in a quick glance then people will open fire (or at least in the states you cant carry a gun in canada)
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