I'm curious as to how other shooters do their group measurements . How do you average / How many shots per grouping ?.

First .
This is how I do my load development. I Select a caliber , bullet weight then several or a few powders . Brass is prepped . I then load middle of the road #5 rounds each of different powders, then additional loadings of # 5 each depending on case capacity load up and down by .5 or 1.0 grains . Like .222 or .223 .5 grain .338 1.0 grain Small large case .

Range 100 Yd. for development . So I may have say 50 -75 rounds loaded .

I start with original middle of the road load.
Shoot 1 fouler , then 1-1.5 minutes apart shoot group of # 5 . Bore Patch the barrel then repeat with loads up or down .

Depending on what I see I'll pick the best powder bullet combo . I then re prep cases load # 15 - 30 of each loading . Range 100 or 200 Yd.
I fire one fouler and shoot # 15 shots total 3 groups of #5 1-1.5 minutes apart as before .
Then measure total group of 15 , per target .
This is how I average my groups sizes .

I now refine the loads by tenths of a grain , once I find promising possibilities .

Do you do it different ?.

On hunting ammo I don't . I use paper results for caliber bullet weight then load # 5 Hunting projectiles and try them at various ranges out too 400 Yd.. MOA at 100 Yd. for hunting is OK for Me .

Shoot Straight Know Your Target . ...

Since my shooting range is now right outside my shop door, I like to work with one powder and one bullet at a time. Maybe with more than one rifle. I start with a clean rifle and shoot a couple of foulers. I load in lots of three until I get some groups that show promise then I go to groups of 5. If I find a sweet spot for one bullet and want to try another of the same weight, I will rarely do another full work up but will rather tweek my sweet spot on the one around to try to suit the second bullet. The same with primer changes. Basically, I try to find a sweet spot with a powder and a bullet. Then, if I change bullets, primers, COL, etc, I am tweeking that sweet spot, not doing a full, start from scratch work up.
If I change powders, I start all over again.
As I have posted before, I don't think a change in primers or a change in your bullet jump is gonna make a one-holer out of a dog. And so, to begin with, I want to make a good, consistant piece of ammo. If I can find a good combo of powder and bullet, then I will maybe jim around with primers or COL's. But if that sweet spot ain't there, it just ain't there and I will try something else rather than beat my head against the wall.
In addition to accuracy, I want my hunting ammo to fit the magazine and feed flawlessly. And, of course, never come too close to max nor touch the rifling.

Afternoon Doc.

I load jacketed bullets for two calibers, 25-06 and 308. The 308s are for AR10s so they are a special case.
The 26-06 is a simple rifle to load for, since it's my varmit rifle. All bullets are 100 grain, powder is IMR 4831, primers are CCI LR mag. I had a 25-06 a number of years ago that I settled all the choices back then. When I bought this Remington I knew what I wanted.
I fire formed all of the cases, after being weighed, throwing out the grossly over and under weight cases, using scrap bullets, those that weigh outside of the 3/10s of a grain norm. The cases are full length resized, trimmed to length, case necks uniformed for thickness, primer pockets uniformed for depth, flash hole trued up.
Now we're ready for loading, each case is primed using the Co-Ax seater, powder charges are thrown and weighed, bullets are seated to just kiss the rifling.
With my rifles, the old and the new, the is right at Max or a couple 10ths below depending on the 100 grain bullet.
Jim