Introduction #

The Acetech AC5000/6000 and Xcortech X3200/3500 are standard measurement devices used by just about everybody on events and review videos. People also use them to check the consistency of the shots of their replicas. But how I don’t see much of a discussion about their accuracy, difference of the readings between serveral units etc. Even the manufactures are keen on providing any details about the accuracy and every measurement device has some measuring error. How bit is it on those chronos? Let’s find out.

The test #

Since I don’t have a well measured, stable, normalized bullets flying around that I could use to test the accuracy, I decided to do the simplest thest I could - shot my shots into two units that sit one next to the other. I didn’t have access to two exact same devices so I have used AC6000 and AC6000 MKII (which I believe only differs in taking 18650 battery instead of 4xAAA) which I hope is close enough. I did two tests - one when the MKII is in front and one where it is in the back to compensate the fact that the BB is loosing its velocity after leaving barrel. Here are the results:

The results #

As can be seen, the unit in front always shows slightly higher velocity and the average difference is 1.84 FPS and 2.12 FPS. This was, of course, expected as there was around 13 cm of distance between the sensors. If we remove this offset from the difference the actual variation is +/- 2 FPS (with one situation where it was actually 3). This is at around 405 FPS so the error is +/- 0.5%. The sample size was quite small, though, so threat this value as a rough estimate only.