Purpose of a chronograph in Bullseye Shooting

First topic message reminder :

I was watching this video (out or curiosity, not because I'm looking to buy), and got to wondering if this type of device is something all (most?)  (many??) of you use in testing loads and deciding what to shoot?

Is something like this used by ordinary Bullseye shooters?

Also, in what ways might it be useful?  Is it to compare the speed of your ammunition with what the books and charts say it should be?

Last, is this used to compare the speed of your bullets with what has been identified as the "best" speed, so you vary the powder charge to adjust the speed?

I hope I'm not asking anything too silly here - I've never seen one of these in person.

I have 3 my favorite is my Lab Radar it gives more data and is easier to set up and use.   The data sure hasn't helped my BE scores.  May have helped getting my bench AR 15 loads down to  1/3 MOA and yes I have checked position sensitive powder.  Most of all I just enjoy using that stuff.  My son says I just love gadgets.  Maybe he is right I do have 4 high end fishfinders on my boat.  Don

Don, if you have three, how are they different?  What makes one different than another, or better than another?  Do all three give the same reading, for the same gun and powder and bullet?

I love gadgets too.   Too much.  I try to keep the gadgets separate from "what's real", which to me means what is called "fundamentals".  But gadgets are fun, so why not enjoy them.  

In my mind, I can shoot an X every time!  I just need to get my body to perform as needed.  Gadgets don't count - they're just icing on the cake, but the cake needs to be perfect.

This is my first one. https://www.brownells.com/shooting-accessories/range-gear/chronographs/prochrono-digital-chronograph-prod5547.aspx  it worked fine and I used it indoors on a platform I could roll it out in front of the line with a push pole as the line at the indoor range is always hot.  I had to buy the light bar and I bought the assy to read the data on my I Phone.   It worked well but I was looking for one that was easier to take to the range and set up.

So I bought https://www.brownells.com/shooting-accessories/range-gear/chronographs/magnetospeed-barrel-mounted-chronograph-prod55606.aspx  Now this fit the bill petty well.  Easy to carry, easy to set up, but didnt work on all my guns.

This lead me to buying my Labradar https://www.brownells.com/shooting-accessories/range-gear/chronographs/labradar-doppler-chronograph-prod109164.aspx  This was the answer to everything

I couldn't get these to post on my previous post.