@Raven Yes. I can tell you from personal and professional experience that it's called RECOIL. The force of the exploding gunpowder ejecting the metal slug causes the rifle to jerk sharply - to recoil - in the opposite direction. In MC's case, the barrel would go flying upwards and backwards pretty fast and he'd find himself holding a fistful of big fat nothing after the first shot. If he was holding it properly, he would have the rifle positioned lower and braced against his shoulder, and it was me, I would also have the bi-pod extended, and sitting on a relatively flat surface. And I wouldn't bother wih a visual scope. Unless MC got super powered eyesight with his extradimensional storage space and can see through the falling, flying snow, he would be much better off using a thermal imaging scope since living people throwing off body heat from the exertion of trekking through the snow will stand out remarkably well against the frozen cityscape behind them, making them much better for his planned target practice.
I've got 109 mangas open in Opera, and have neither the time nor inclination check for your comments and retorts, and if I had a signature, I would probably put it here instead of whatever this is.