I don't worry much about the absolute value given by the IR gun. Assume it's wrong.
I care about the consistency of the value.

If it shows 180 degrees when the object is 170 degrees it's not that big of a deal. This assumes it shows the temp to be 180 degrees every time the object is 170 degrees.

If it shows the same difference in temp it's good enough.
Shows 190 when object is 180.
Shows 200 when object is 190.
And so on.

That's all you need.

A radiator should have about a 30 degree drop in temp from input to output. That's the concern. Finding differences in temperature.

I know my IR gun is off but it showed me the big temp difference between the water pump housing and the upper hose. BINGO! Thermostat wasn't opening. Overheat problem solved in seconds. Power Tour resumed.

The same car had an issue with overheating at idle and I fixed it with a large clutch fan. The car was using the stock fixed fan and no shroud. It simply wanted more air at idle.

The father and son team who drove that 71 Charger in 2012 came back for the Power Tour in 2013. They still had my clutch fan in place.