What is accuracy?? What do you expect, what will a off the shelf Mosin do?
First of you must realize that "Enemy at the Gates" is a movie, granted, based on a real event as portrayed in the book, "Notes of a Russian Sniper", by Vassili Zaitsev. One must understand Military Snipers are not taught Head Shots, but center of mass, body, or the biggest target the enemy produces. This is portrayed in Zaitev's book, and confirmed in Joseph Pilyushin's book: "Red Sniper on the Eastern Front".
If one was to find a stack of Mosins at one of the box stores like Cabala's, Schells, etc, you can pick through the racks with a bore light, find a clean bore and find a fair bore. Clean it up and find some decent ammo and you can realistically find it will shoot 3 MOA groups.
Now we know the average person's size, shoulder to shoulder is right at 19 inches, (thats where the Army came up with the size of the E-Silhouette Target).
So we have a 3 MOA gun, and a 19 inch target. What does that mean. Assuming you can shoot as well as the rifle, you should be able to engage targets to 633 yards. Even if you only can get a 4 MOA Rifle, thats still 475 yards, thats beyond the average Military Sniper shot.
OK lets get realistic, we're not snipers, we shoot in competition, or plinking, Whatever, we shoot for fun.
The place Mosins and other vintage Military Rifle are fired are CMP GSM Games, or Vintage Military Rifle Matches, These are fired at 200 yards. The X-10 ring is 7 inches in diameter. If you have a 3.5 MOA gun you should be able to clean the targets. Even if you have a 6.5 MOA gun you should be able to keep them in the 9-10-X ring so we can assume you can fire 95%, (respectable and a winning score in most GSM matches).
The CMP Vintage Sniper Matches (using pre-1954 Sniper Rifles) use the 300 & 600 Yard NRA High Power targets. Again a 3 MOA gun is capable of cleaning those targets.
The thing is, you don't see that many cleaned targets at GSM Games, why?
My contention, if you want an accurate Mosin (or any other rifle), PRACTICE, dry fire and put rounds down range.
Accuracy isn't the rifle, its the shooter.