After years of reloading without one (middle of the road loads for hunting and plinking), I have decided to squeeze some money out of the budget to buy a chronograph. I can do my own statistics and can write down my own values so a bare bones system is what I am looking for. But there are a number of systems out there. What should I in particular LOOK OUT for in a new system? Are there some quirks not generally known by the first time buyer?