Thats becuase 2x4s arent really 2x4s.
As I understand it (which could be wrong), boards are initially cut to 1x6, 2x4, 4x4, ect. but the cuts are so rough that they are sent to a plainer. This shaves off a little bit off each side, making the demensions slightly smaller than original. For example, a 2x4 is really about 1x5x3.5.
Reguardless, if a bullet is going to blow through 1.5 inches of fairly sturdy wood, then it is definately enough to blow through a ribcage, sternum, or skull assuming odd angles arent present.
Last edited by Glock19Fan; January 15, 2013 at 10:36 PM.