Dont try to calibrate your real gauge to a IR thermometer, if you want to do it properly use a contact thermometer. IR thermometers are an indication only and should not be relied on as you will get a different temperature reading on different materials, surface finish makes a big difference as does the presence of scale /paint/corrosion. Its amazing how a bit of technology in a gadget makes people thing that it must be somewhat better than what we had in the past, you need to understand the devices limitations and use it accordingly