I have been struggling with this a bit myself, since the only people apparently willing to discuss groupings on the internet are sharpshooting cyborgs who punch the X off a target at 500 yards offhand, or experienced bullseye shooters who are genuinely super-talented but can't necessarily do much to help a new shooter.
For myself, this year I've been taking my pistol shooting more seriously and trying to improve. Towards this end, I've found the only real meaningful way to tell how well you're doing is to record your results and compare things over time. I now keep a 'shooting log' in a little day planner. Reference:
Every time I go out and do some pistol work, at the end of each session I shoot a five-dot target (a dot in each corner plus a bullseye). That's my 'evaluation' target. Then, I go home, pull out a tape measure, and record by best group, worst group, and mean of my five groups. I fold up the targets and keep them in the book. Next time I go out, I do the same thing and compare. I throw out last week's evaluation targets. In four sessions, my mean groups have shrunk almost 1". That's pretty good for only four sessions, I think. Part of the improvement is from having a clearly-defined goal. It's helped me a lot, even if it does make me a huge nerd.
Sometimes I also record even more data, like how much I shot overall. I also write down anything I notice that's really obvious, like improvement with difference stances (I like Weaver better with my revolver for some reason!).
So, if you really want to improve, I highly recommend doing this, it's working for me. The only way you can really tell what's a 'good' grouping anyway is by comparing your own results. Some people are just naturally better than others. I freely admit to being an awful shot with everything I pick up, so for me to exclusively compare myself to others with more natural ability is just a shortcut to frustration. Validate results by improvement instead of measurement against other people. This isn't to say competition isn't useful (an fun), but for something you can really analyze, personal improvement is the most important benchmark for newer shooters like you and myself I think. I'll worry about outshooting other guys in competition later.
Also, starting with a .40 is pretty bold haha!
