How near would a 16th century musket's muzzle have to be for the shot to go through skull bone?

Question

An ancient Inca skull shows a hole made by a conquistador's musket shot.

http://macrocosm-magbook.blogspot.com/2007/06/hole-in-inca-skull-caused-by-musket.html

Answer 1

Depends on the purity and dryness of the powder, mass and shape of the ball, angle of the shot, windage, length of the barrel ... approx 50 yd or less.

Answer 2

I would say the same fifty yards or less, probably less after seeing the Discovery "fastest guns in the West" series.  

   At fifty yards the old saying "hitting the side of a barn" fits the standard here, they had a hard time doing just that, hitting a square six feet square at fifty yards.

   Then, the "ball" didn't penetrate the one inch ply board.