Quote Originally Posted by DeltaII5 View Post
http://www.theboxotruth.com/docs/bot16.htm

This is the one where he tests rounds on the "shootpacks." It's very interesting how 9mm flattened out on the 3rd sheet, 40 cal on the 2nd sheet.

The soft armor "shoot packs" has 28 layers in it. Just like normal IIIA armor.

Even though most of us don't wear body armor around on a day to day basis, it's very interesting to see how ineffective handgun rounds are at penetrating.
Good link, Delta. The Box 'O Truth is a great site, if for no other reason than the sheer amount of ballistics data they've gathered over the years.

Quote Originally Posted by Farbmeister View Post
Didn't the box-o-truth test HPs and found that denim would cause a failure to expand and significantly reduce penetration?
I believe the Box 'O Truth people did validate this theory. However, this is actually a design flaw inherent with JHPs. Although some do a better job than others, in the end ALL JHPs do not expand as well (in comparison to direct impact with raw flesh) when there's any type of cloth barrier, which there usually is.

Put on your thinking caps folks:

This is because JHPs, by design depend on a fluid dynamics principle, hydrostatic pressure, in the cavity of the bullet head to expand. This pressure is easily obtained when the bullet impacts any soft tissue, gelatin, etc. because the force of the impact essentially causes the material to flow and create the needed pressure. Cloth, however, does not exhibit fluid properties. On impact if a piece of cloth, denim, etc. gets lodged in the hollow point, it can prevent the soft tissue (flesh) behind it from entering the cavity and creating the pressure needed for proper expansion. In essence, the cloth can "clog the hole" and prevent expansion.

Citations:
http://encyclopedia.quickseek.com/in...nal_ballistics
http://en.wikipedia.org/wiki/Terminal_ballistics