My experience with longrange RB shooting stops at 300 yards, but when I hear claims, historical account or any other reference to 400 yard shooting, I have one reaction: Show me. Hit the mark consistently, heck even estimate the range accurately, and I'll believe it. Otherwise I read it as pure horsepucky. Sure a guy might get lucky with a one shot hit, but take that kind of luck to Vegas and make your fortune.
I base all that on my observation that as range stretches beyond 250-300 yards, velocity drops to the point that RBs start to veer and wander. I've heard it explained like a "nuckleball," and that sure makes sense based on what I see on the backstops. Add in the potential for wind drift on the slightest breeze, even minor errors in range estimation and rainbow trajectories....... Like I said, make a one-shot hit at 400 yards and take that kind of luck to Vegas and get rich.