What happens when you use a 250 watt hps bulb with a 400watt hps ballast

i have a self ballasted reflector thats 400watt and i put a 250wat bulb in it and it lit up for 20 minutes until i shut it off. Is this safe?
brooklyn420 Reviewed by brooklyn420 on . 250watt bulb to a 400watt ballast What happens when you use a 250 watt hps bulb with a 400watt hps ballast i have a self ballasted reflector thats 400watt and i put a 250wat bulb in it and it lit up for 20 minutes until i shut it off. Is this safe? Rating: 5