Have Remington 700 in 222 cal.. Wanted to remove open sights, plug holes in barrel with reciever plug screws and install scope. Cannot get screw to start in one of the rear sight holes. Would like to chase threads with tap but am not sure of what size to order. Would someone happen to know the size? Also the reciever plug screws do not screw down as flat with the barrel as I had thought they would. Could I also order a better type screw for the sight holes in the barrel?