Audio problem: We see a Russian commander giving the order that one person gets a gun and a second follows him - the audio is out of sync. It is not another person giving the orders that we can hear, as we prominently see him shout with a megaphone. (00:09:45)
Audio problem: When Danilov is reading the article to Vassili, we see it from a long shot. However, his lips didn't move. (00:20:40)
Chosen answer: Vasily Zaitsev (Jude Law) uses a 7.62 x 54mm Mosin-Nagant M91/30 rifle with a PU scope. Major König (Ed Harris) used a 7.92 x57mm Mauser Karabiner 98 K with scope. Law's scope was wrong as the model used in the film wasn't available until after the Battle of Stalingrad.
Grumpy Scot