temp guns measure surface contact temps, this is a little different than ambient temps. most laser guns have a +/- of 2-3 deg. also. i think temp guns are great for multiple quick checks and basic general temp readings.
the accurites are also +/- 2-3 deg. about the same accuracy, but read ambient(the unit) and surface temps (with the probe). also good for basic temp checks.

imo, i put my trust in good quality proportional thermostats like helix. the UL listed working accuracy for these units is less than one deg.!!

to double check these stats, you really need a thermometer that is UL listed for better than 1 degree +/-.

i have a few thermometers for work that do quite well, when testing out setups and stats and bators, i found the accurites to generally be within 2 deg of the actual temps. pretty good for 10 bucks!!

if you really want to get down with accuracy and temp readings, look into thermometers made by fluke(not fluker), cooper-atkins and hanna instruments. the thermocouple or thermistor probe models are quite accurate


vaughn