I do 200 yards with my handguns so I can't see why 300 wouldn't be a feasible goal.
I have heard it said one should never expect such accuracy from a handgun. I know "Hickok" on Youtube has hit his target with a Glock .23 40 caliber at 230 yards. Should that be considered as very unusual? Or do you think we should be shooting much more accurately than we do?