Drywall follow up
A while back there was a lot of talk here about over penetration of various self defense rounds. Many opinions were advanced about the “safest” round to use if you had good guys on the other side of the wall that the gun was pointed at. One of the posters said something that struck a chord with me. He said “how do you know that the 223 penetrates more than a handgun round unless you have tried it. So I decided to find out for myself.
First I wanted to find out how many walls it would take to stop a bullet. The short answer is many. I made up a jig to space small pieces of drywall 3.5 inches apart. (The thickness of most interior walls) I found many hand gun rounds would shoot through a small house (sheathing, insulation, four walls and maybe more sheathing depending on the load) unless they hit studs, wire, plumbing, etc. Shotgun pellet penetration varied from one wall with birdshot to about the same as a normal JHP handgun bullet. Basically anything that would remotely be considered for self defense* will shoot through several walls. Even an air gun pellet will shoot through one wall, 22 shorts will shoot through several.
It was obvious that a piece of drywall didn’t slow down a bullet much. I wondered how much velocity remained to endanger the person behind the wall. So I set up the chronograph behind sheets of drywall to try and measure that. The problem is dust. A piece of sheetrock maybe a cubic inch in size is turned to dust at the shot, and this goes everywhere, including behind the bullet, and screws up the chrono reading. The velocity varied from a little higher than muzzle speed to losing about 800 FPS. So no numbers are to be relied upon. I tried using FMJ bullets and rigging up a cardboard shield to keep the dust back, but none of that worked.
So my simple conclusion is to never depend on a wall for a backstop.
The pictures are the setup for the chrono, and the differences between entrance and exit on the boards.
*The one possible exception to this is if you consider birdshot suitable. I no longer do, but some have faith in it.
After typing this, I thought of something that now seems obvious. When you shoot drywall, a cloud appears behind it that is the source of the chrono problems. So why don’t I move the chrono way back so the bullet has a chance to shed the dust? If I get the time I will try this.
Hope you found this useful or at least mildly interesting, Griz