The post by RW Smith on testing loads caused me to go find my crib sheet on a verified ballistic testing system. The system uses water filled milk jugs and was verified accurate by comparison testing with 10% ordnance gelatin. This was written up in a national publication, I'm not gonna excavate my files looking for when/where. That's why I have the crib sheet.

Method:
Milk jugs filled with water are lined up firmly touching, straight & level. (I use a 2x4 base to help on this.) Some jugs have an expansion dimple in one side, you don't want that in the bullet path. Having the handle at about 10:30 on the clock avoids this. Obviously, you have to aim so the bullet passes through the lower part where there's all water. You want to make sure you're not shooting through the jugs on an angle. Be very careful you're actually shooting level with the jugs.

Now then, the expansion-or other behavior-you will see is exactly what you'd get in ordnance gelatin. Penetration is another matter. Your correction constant is to divide the penetration by 1.55. Each jug of water completely penetrated is 6 inches of penetration.

Now then for the jug the bullet is found in, the penetration is given as the following:

No mark on the back of the jug, +3 inches of penetration.

Marked on the back face of the jug, +6 inches of penetration.

Broke the back of the jug, +6.75 inches of penetration.

Broke the back of the jug and marked the wall of the next jug, +7.5 inches.

Broke the front wall of the next jug, +8 inches.


Example: bullet passes through 3 jugs, breaks the back of the 4th jug and marks the wall of the next jug. Penetration is 3 x 6 + 7.5 /1.55= 25.5/1.55 =16.45 inches of penetration. Expansion is what it is.

WARNING: if you're gonna do this, wash the jugs out thoroughly when you empty them. Otherwise, you get mold that will become airborne when you test. Breathing that isn't a good idea. You'll also want some distance between you and the jugs when testing magnums or .223/5.56 mm. Like about 30 feet.

BTW, one of things you're gonna learn is that not all bullets travel straight when they hit the test medium.

When testing SD Hollow Points for expansion and penetration, it is common to use two layers of blue jeans material on the front to simulate clothing, avoid buttons and zippers.

Some HP's just clog with cloth and behave like FMJ's others are caused to over expand and shed weight. This is where jacket wall thickness, exposed lead nose, and the addition of a hollow point really show the differences! When Hornady brought out the XTP bullets, they discontinued the SP & SP/HP in 357 & 44. Not really a big deal for people size penetration, but on large deer and wild pigs it made a huge difference. In the old days (When Frank Barns still owned Barns Bullets) almost any bullet to be used on something that could eat you the jackets were offered in two or three different wall thicknesses! Think about it: Cape Buffalo have tougher hides and muscles than Lions do, and yet lions can and do kill and eat Cape Buffalo!