It is getting to where half inch at 100 yards is getting fairly common for high quality weapons.
I have never done any long range shooting but once was surprised that my old 98-09 Argentine Mauser was pretty easy to hit with at 400 yards.
The rifle was unbelievably well made and I got it unfired with the original test target. Herr Ritztmann of DWM, Berlin, had fired a two inch group at 200 meters with iron sights. He then signed the target. I noticed the test target which was shot in 1909, had an aiming point and then the group was on a square around 3 inches higher than the aiming point.
The sights being on at 400 yards made all the difference in the world.
After 400 yards all kinds of problems arise. Among them are heat waves, wind drift, accurate distance measurement, temperatures, and I am sure, much more.
Some “old school” caliber rifles were built exceptionally well. I have a Weatherby in .308 Winchester that came with a three-shot test target that looks like two shots that overlap each other - until you look REAL close.