300m? Airsoft guns can barely shoot 90m lol
Also, lasers work BOTH ways, if you can see the dot on your target, your target and everyone around him can see YOU.
Besides, given windage and hopup, brush, gusts of wind, hop variations, etc. You're basically just never going to be able to hit that dot at 90m.
It's best to just learn how to shoot people with a scope, since at those ranges, you really do have to watch the BB to see where it's going.