Yup, you're right, black green black gold gives you a 5ohm resistor with a 5% tolerance.
If you're going to drive your LD at 250mA you're going to need a 1/2 watt resistor. When using the LM317 you calculate the wattage of the resistor needed by multiplying the current by the LM317's reference voltage. i.e if you want to know the wattage of the resistor you need to drive your diode at 250mA you multiply the reference voltage (1.25) by the current (.250) which equals .3125 watts, so you need to use at least a 1/2 watt resistor to run your laser diode.
And of course a 20x diode is better, a SenKat diode running at 250mA will output between 150 - 180mW, but when running a 20x diode at 420mA and using a glass lens you can get an output between 280 to over 300mW.
If you're going to drive your LD at 250mA you're going to need a 1/2 watt resistor. When using the LM317 you calculate the wattage of the resistor needed by multiplying the current by the LM317's reference voltage. i.e if you want to know the wattage of the resistor you need to drive your diode at 250mA you multiply the reference voltage (1.25) by the current (.250) which equals .3125 watts, so you need to use at least a 1/2 watt resistor to run your laser diode.
And of course a 20x diode is better, a SenKat diode running at 250mA will output between 150 - 180mW, but when running a 20x diode at 420mA and using a glass lens you can get an output between 280 to over 300mW.