I have been shooting the H&K 91 since 1977.
For over 23 years I was a LEO SWAT Sniper.
I have also shot in IPSC, Sniper rifle matches, Service Rifle, PALMA, and 1000 yard Any, Any rifle matches.
I have hunted a lot with an H&K 91.
I do not consider a standard H&K 91 to have Sniper Rifle quality accuracy.
I DO consider it to have Semiauto rifle, precision rifle accuracy.
Here are some random thoughts, baised on my actual shooting of the H&K 91.
I have shot deer, pigs and antelope as far as 350 yards with no misses, using a scope of course.
Head shots at 100 yards, no problem.
I have shot hand sized groups at 400 yards many, many times.
With a 3.5 to 10 power Leupold scope, using Federal 168gr match ammo, I have had no problem hitting chest sized targets at 850 yards, as long as the wind is not too squirrely...
You can shoot a 5 round group at 100 yards, then shoot 40 rounds rapid fire, and then shoot another 5 round group, and your point of impact, and group size will be the same as your first 5 round group, ie NO Zero shift.
I do not know of any out of the box ParaMilitary semiauto rifle that will do anywhere near as good as the H&K 91.
So while at 100 yards it is not as accurate as a "Sniper Rifle", once you get past 200 yards, and might need to shoot fast, its advantages start to show themselves.