The problem of 3 and 5 shot groups are they're statistically too small. An average 3/4" 3 shot group can be 70% smaller or 70% bigger. So it could be 1/4" or 1 1/4". With the same load under the same conditions. A 5 shot 3/4" average group could be 50% larger or smaller, so a 3/8" group or a 1 1/8" group. The bigger your sample size, the better average group size.
I could cherry pick 3-5 shots out of that 10 shot average and get 3/4", that doesn't mean the rifle will do only that every time. If you noticed, I am happy with the rifle, it might not be in a cartridge I like, but I'm not upset with it's performance either. It's a utilitarian rifle shooting respectable utilitarian groups. I'm happy with it.
Back in post #35 you wrote, “…..If I were to shoot 5 shots instead of 10, some of these groups would have been 3/4".…..”. So clearly you were getting ¾” groups from some 5 shot strings and then those groups opened up as you continued to add bullet holes to the group.
I'm not suggesting that you cherry pick 3 or 5 bullet holes out of a larger number of bullet holes to get the group size you want. As you point out, that would just be a confidence builder and not a true evaluation of the rifle’s capability.
Any measurement of a rifle's accuracy derived from a sample (like say 5 shots) is just that, a sample. A bigger sample size may be statistically more precise than a smaller sample size, but we’re pretty much stuck with extrapolating some measurement of a rifle’s accuracy by looking at fairly small samples of that rifle’s accuracy.
Most people use 3 or 5 shot groups to get some idea of a rifle’s potential accuracy. Yes, a bigger sample size (like say 10 shots) would be statistically a better yardstick. It would also take more time to avoid heating the barrel and it would consume more ammunition.
A larger sample size would be better in terms of evaluating the rifle, but a smaller sample size is likely good enough. A 100-shot group would be statistically a better sample than a 10-shot group but it wouldn’t be very practical. A 5-shot group probably isn’t the best yardstick, but it is a fairly common yardstick. If you like 10 shot groups as your yardstick, then great, that’s your yardstick.