Originally Posted by JTJ
There is also a thing called momentum. It is harder to stop a heavier bullet. Also 1300 fps is a +P even for a 135 grain in a 4" barrel. 155@1300 is 10mm territory. The interim load for the FBI while they were doing their testing was the 9mm 147 grain. Bullet design has come a long way since those tests but laws of physics have not changed.
A 405 grain 45-70 will out penetrate a 308 150 grain twice as fast.
Many of us believe that momentum is basically a meaningless measurement in bullet effectiveness. Old timey Jeffie Cooper nonsense.
I realize there are those who believe that gross over penetration is necessary. I'm not one of them. IMNSHO, 10-12 inches in bare gelatin is adequate. Rapid expansion is far more important. LE requirements are a bit different.
You and I are not shooting through car doors or windshields. Police are paid to be out looking for trouble, you and I are (or at least SHOULD BE) trying to avoid it.