i dont know if you know how a chrono works there all the same if anything you pay for the brand name and shell all a chrono is is to lasers at a set distance when the first laser is triped it starts a simple clock when the bb pases through the second one it stops the timer there all the same if anything if it reallly was a crappy chrono your gun would be shooting at a slower fps
that's not always true. There are tons of different types of chronos.
There are the three main kinds you see used for airsoft... external optical, internal optical, and internal laser.
External optical types use sunlight over two larger light sensors, and are sound-activated... so if it's too dark, or you have an extraordinarily quiet gun, it won't work (a TM mark 23 with the silencer would NOT chrono on these. lol... we tried), and they aren't as accurate as some other methods.
Internal optical are basically the same thing as the external optical, but a tube with basically two flashlights on them. Same principal as above, with the same cons, except it can be used in the dark.
Internal lasers then take it a step further and use higher powered lights (sometimes outside of the human vision spectrum... most don't actually use lasers) over smaller light sensors. These are more accurate if you shoot straight through, but if you fire at any kind of an angle, the effects are magnified in these. Don't believe me? Go grab a madbull chrono and shoot straight through a few times for a baseline reading, then angle the gun as much as you can. You should get about a 40fps swing.
The smaller it is, all else being equal, the less accurate the chrono.
The larger the sensors, all else being equal, the less accurate the chrono.
So, no, they aren't all the same.
Also, there are the radar chronos you RARELY see in airsoft, although they are much more common in paintball. They have two semicircular sections held onto the chrono by thin rods. They are very accurate and very bulky, but are also capable of measuring extremely high velocities (such as those used in firearms) very accurately. And there are radar-gun chronos... used almost exclusively in law-enforcement, baseball and professional-level paintball, where you can point it at a moving object and get it's speed. Yes... a cop's radar gun is a chrono!