sniper weapon control error budget analysis
http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA367672
This is quite tech. but go to page 32, table 7: Read the base line col. ref PH (probable hits), come down to 600 yards. I used 600 yards because that is the distance (in addition to the 300 yard line) that the CMP uses in their Vintage Sniper Matches. Go to the CMP web site to find the results of the matches.
There is a lot of information in the Report from the Army Research Lab. I used the Baseline because it most closely resembles the course of fire for the Vintage Sniper Matches. The Baseline in the report consist of: 2 man sniper team, using Rifle, Spotting Scope and laser Range finder. The CMP games don't require the range finders but it's a known distance range.
As to range finders, when I was running sniper schools we didn't have them. We used the front sight of the M1. The Service Rifle sight on the M1 is the same width as the E-Silhouette Target at 250 yards. Using that, you can effectively use it as a range finder, much the way Mil Dots work.
The front sight on the average Mosin Rifle is .060, using that, and converting it to MOA, (figuring in my head cause I'm too lazy to find a calculator), the Front sight would cover the E-Silhouette at about 300 meters. If you understand that, then you have a range finder built into your rifle. I don't have the experience using the Russian Scope to tell you what the MOA of it's post is.
Anyway, this and my other post, is to point out, that it's not the rifle, its the shooter.
The average sniper shot in Vietnam was just north of 400 yards. I've shot enough Infantry Trophy Matches at 400 yards with a M16A1, using M193 ball that I know I can hit a E-Silhouette at that range with iron sights with regularity. If I can do it with a M16A1 and 55 grn bullets, I've no doubt that anyone with a bit of practice can engage the same target at 600 using a Mosin.