And Colonel Whelen thought a rifle that grouped into one inch was truly exceptional, although this is based on ten shot groups so still may be true.
Yes, he generally shot 10-round groups--but it was also unusual to find a rifle that would put them all into an inch, or close to it, when he started writing over a century ago. Improvements have been continuous since then, including bullets, powders, actions, barrels and bedding. Oh, and scopes!
I usually use 10-shot groups when testing prairie dog rifles, but not so much to determine accuracy but see how they react as the barrel heats up--which they always do on a big dog town. It's common for many of today's factory rifles to put 10 in 3/4" inch or under, right out of the box, even with factory ammo--and sometimes even less.
