No matter how much data you enter into a hand-written log book, it won't be nearly as useful as a spread sheet when it comes to understanding what your data actually means. Gathering data is one thing. Understanding it is something else.
For example, what is the average Mean Radius of your ten best 5 shot groups using Varget with Berger VLD 80gr bullets compared with the average Mean Radius using Vihtavuori N-140? Rather than spend a week reviewing a dog-eared log book you can have the answer to this question in a few seconds if your data is kept in a spread sheet.
I believe you can't get where you want to go unless you know where you are. And the more precise and organized your data is, the more you will know about your present situation and how it compares with past performance. From there you can steer your efforts in the correct direction to make those tiny improvements we're all constantly searching for.
I scan all my test targets as well as my BR targets using On Target software. I make an Excel worksheet for each session. I also copy the information into a "master" spread sheet for that particular gun so that nearly all my groups are in one group. Then I add in additional information about powder types, bullet weight, recipe ID number, etc. It looks something like this:
Sample Excel Chart
With a few key strokes I can find out what's best, what's worst, averages, and so on using most any significant parameter. I can count how many rounds I've fired if I want that information. I can easily see how many 90gr VLD's I fired from this barrel if I want to.
In other words, logging data is a good thing; however, unless you can easily study the data, sift it, sort it, and look at it eight-ways-from-Sunday it's not doing you all that much good.
Once you get the hang of it, you can log digitized data from a session at the range as quickly as filling out a log book. And you can do the measurement and calculations MUCH faster. What's more, you can do all of it after the fact so you don't have to spend any time in between shots writing or chasing your log book that the wind just blew away. But the best thing about keeping digital data is that you easily get a measurement of your vertical and horizontal group size, deviation from the aim point, and Mean Radius too. Mean Radius is considered by many as more important than group size. It's tedious to measure and compute by hand, but On Target does it automatically. You just click your mouse on the scanned bullet holes and bingo, you have just what you're looking for. Add a few notes and you're on you way to becoming the World Champion you know is locked inside you................... somewhere.
Give On Target a try.