Can a .50 BMG travel nearly 5 miles?

... as the VPC and others have been known to say?

Yes, technically a .50 BMG round can travel 4 2/3 miles, but only if you fire it at a 38 degree angle, like a mortar. (Try finding a scope you can adjust to 38" elevation.)

Of course, since it's coming down at a very steep angle, it would be difficult to hit the target accurately, and the speed and energy are greatly depleted.

Not to mention: If you're shooting at a moving target, you'll need to lead it quite a bit, as the flight time is nearly 3/4 of a minute.

Data source (pdf)

In a vacuum, the optimum angle for maximum range would be 45 degrees. In air, it works out to 33-38 degrees, depending upon the caliber.