I have two SKS's and am very impressed with their performance over irons. I have not fired either past our 200M range. I zeroed my last SKS about a month ago with my wife spotting. I set my rear sight at 200M and proceeded with my sight tool to produce a 200M zero with '63 Bulgarian surplus. After shooting the crap out of a tiny bush in the backstop for around 30 rounds, I went back to a 4" bull on the 100M.
Slide the rear sight gingerly to the 100 stop and proceeded to fire 5 into the bull with a six o'clock hold. After viewing the bull through the spotting glass, I was much impressed to see all 5 into about 3-4" right at POA, on the 6 o'clock position.
Nice to see a service rifle, it's sights, and it's intended ammunition,.. all working together as a team to produce predictable results.
I would feel very much threatened at 400M with an SKS aimed my way in the hands of a marksman's level shooter. Now a USGI M-1 carbine, of such I've fielded two,....if you hold still and try not to move around too much,..you're probably good to go at 400.
I am NATO

/Allies Rifle first as a collector and shooter for that matter, but have found a big respect for the lowly SKS that I once scoffed at as a "shotgun pattern bangstick" wielded by a mutant, socially and physically deformed illegitimate enemy in the Eastern Bloc. And all that cheap musty smelling surplus ammo , yummy!
......you are now returned to your Radio Moscow broadcast, the Voice of Mother Russia, already in progress...........