Note that the grouping itself was concentrated in one quadrant of the target circle itself, which indicates his sights were not precisely set. This is an even greater accomplishment in that regard.
With manufacturing getting better and better, accuracy will only get better along with it. Rifle and bullet combinations that produce minute-of-angle (MOA) accuracy or better used to be hard to find. Nowadays, MOA rifles are pretty common if you spend the money. I've got a 5 yr old .308 tactical rifle that shoots about 1/2 MOA, and my wife has an AR10 variant in .308 that she just bought that will just about use the same hole at 50 yards. And, that gun is a semi-auto!
“Note that the grouping itself was concentrated in one quadrant of the target circle itself, which indicates his sights were not precisely set. This is an even greater accomplishment in that regard.”
Precision is the ability to replicate a result. Hence the tight group indicates great precision.
Accuracy is indicative of proximity to actual value. So it is the accuracy that needs to be set in this particular example. An instrument can be precise while not being accurate (the case here), the converse is not necessarily true.
I’ve worked in engineering where we were drilled in the proper nomenclature for instrumentation. Sorry if off topic, I can’t help myself.