Question is which one to buy? I googled and read reviews seems one said this or that one is great other say it is crap. I shoot on outdoor range looking for one that has a remote so when it is shot I don't lose everything. Like to keep cost under $150.
i have used several Chrony's and now use a CED M2. Both brands all of the units worked fine. Other brands work well as well.
All of the chronographs have some idiosyncrasies that cause erroneous readings. Once you learn those, you will get excellent results. Most of the problems have to do with the sensors missing a bullet due to sun light, no sun light, reflections off the ground, reflections off the bullet, and more. The Chrony instructions, at least, have some good trouble shooting aids in this department.
With my M2, I have added the infrared lights and now have fewer sensor errors. It is less sensitive to ambient light issues.
The units seem to perform better with a fresh battery. I would only change batteries when things did not seem right, maybe every fourth or fifth use over the period of a year. Battery life depends on how much you use the chronograph so it is prident to keep a fresh spare on hand.
The price the unit will determine what extra features you get. The basic Chrony, or other basic unit, with a pencil and paper will get the raw data and maybe some calculations (average, high, low, extreme spread, etc) but you will have to write them down.
The more expensive units calculate more, remember strings and maybe even printing out the data.
Getting a unit where only the sensors are in harms way is a good thing but repairing/replacing pieces is not inexpensive. Not as expensive as a whole chronograph, but not just a few bucks either. A sensor array usually gets damage when the operator gets rushed or sloppy. So, take your time. Remember that rifles have an offset between the sight and the barrel.
I have shot out two Chrony's. I still have the third but use a CED M2. The M2 allows for direct downloading of the data to a computer, which I like.
But, a pencil and paper helps keep the purchase costs lower.
Hope this helps.