I've always wandered how can we tell which of these guns are the most accurate and consistent! I have 2 exergen IR guns. The 'old' flat square unit and the newer version. Both measure my nitro engines and give the same reading +/- 1 degree. Now this to me gives me some confidence that they are at least calibrated the same and the consistency is there. Ive not tried it against a cheaper gun but I'd be surprised if the accuracy and consistency is the same as the exergen? Its probably close enough at a guess...
The Harbourfreight is a nice find nonetheless and is a good option to those on a tight budget!