Every serious firearms hobbyist needs a chronograph. When you're reloading and looking at the figures in the books, you're never really certain what velocity you're getting out of your load, in your gun, through your barrel.
A good chronograph is fairly inexpensive, running from a basic one at $80.00 to a top of the line at over $200.00. A chronograph will tell you lots of things, like bullet velocity, high velocity, low velocity, average, standard deviation, and extreme spread. I use mine several times a year when I'm working-up loads.
There is just one problem with owning a chronograph and that's this one. Eventually, you're going to shoot the darned thing.
I frequent a forum entitled The Gun Counter and contributor Felix sends us a picture of his chronograph, in demotivator format.
Nice group. I don't know what he was shooting, but he got it, for sure. I've shot mine, one shot with a .30-06. The basic rule for chronograph owners is that if you've never shot your chrony, you will shoot your chrony.
Thankfully, the Chrony folks are very understanding and have excellent customer serice.