Actually, I've heard Peter Kokalis state that the Dragunov was a mass-produced field-issued marksman rifle, not a true sniper rifle, so is it a surprise that it's not all that accurate or long-ranged? It's a sharpshooter's personal weapon intended to give a squad some punch a little distance beyond standard rifle range.
It may have been 'intended' as a squad based system, but its employment in that role deviates regularly. (probably because the first priority of *any* sniper is another sniper, and travelling around attached to a big, noisy, squad would radically decrease the sniper's chance of survival.)
I have to revise my accuracy quote, though. According to Maj. John Plaster, the conventional wisdom gives the Dragunov, on average, 2 MOA! That's not a 'sniper' rifle by our standards which demand 1 MOA at minimum, and tend more toward 1/2 MOA as the norm.
So unless 'Juba' is employing his rifle as a 'powered' bayonet, I think this claim of shooting between armored plates is either dumb luck, or el torro pooh-pooh.