There are two things we want to know in doing terminal ballistics testing and that is both expansion, and depth of penetration. You can find out how much expansion a bullet fired at a given velocity at a determined distance by simply firing into sand bags. Lead, and even alloy lead and copper jackets perform fairly uniformly in this medium, and from observation of recovered bullets from animals, expand much the same.
However, penetration is quite another thing. Ballistics gelletin is probably the best medium for comparing expansion, particular when shooting thin skinned targets such as human torsos. There are enough expanded bullets recovered from human bodies, alive and dead, to know how deep bullets travel through human flesh. The same is pretty well known with light skinned animals like deer.
The problam for such research has always been with predicting penetration on heavy boned, thick skinned animals. Tradition has it that only solid, large caliber bullets going at moderate velocities can be counted on fully penetrating something the size of a large bear, or buffalo. High speed, light weight bullets, that are designed to expand rapidly do not do so well. We all pretty well understand and know that. Its everything in between that gives us pause or pulls hairs!
Over the years I have tried lots of medium for testing penetration and expansion. It took awhile for me to figure out I get more predicatble results if I don't try to do both at once.
If you have never killed a deer with anything, then find a friend who has. See if he, or someone else he knows has kept a ball or bullet recovered from the dead animal. Then ask about the original caliber, load, and distance to the animal when it was shot. Pick your penetration medium. Use logs if you must, but I have used boards to good effect, as well as wet newspaper, dry newspaper, etc. Borrow the friends gun and load the gun with the same load he used to shoot the deer. Fire it into your test medium. You know that particular load did not penetrate the deer, and from his description of the wound channel, you also know approximately how far the ball traveled through the deer. Use that as your standard for comparing everything else.
Once you have that comparison standard, any medium you choose is likely to tell you within a few inches just how far a particular ball or bullet and load will penetrate flesh. I found, after much testing, that penetration was more a function of the weight of a ball or bullet, than its velocity, as the old rule, faster bullets slow down faster seemed to work on penetration tests, too.
As for expansion, I believe that the reason the ball did not expand in the live aspen tree is because the tree was ALIVE ! I fired a .45-70 405 grain bullet into a fresh elm tree stump at approx. 15 meet, and the bullet penetrated about 17 inches, but only 13 inches in a straight line, about 2 inches into the tree, the bullet decided to follow a growth ring and made an arc around the tree. The bullet did not expand. It was about 1/8 inch shorter, and was reduced to .43 caliber, but you could still see the grease grooves. Velocity was at 1200fps. I have recovered that same bullet, using the same load from dirt and it mushrooms very well. I have seen similar bullets removed, or recovered from, large game, and they also were mushroomed.
My conclusion is that live trees often resist bullet expansion, UNLESS you are shooting a high speed bullet, designed for quick expansion with a hollow point, or hollow nose construction. At the very least, you should fire more than one bullet into a test medium and look at your averages before making any conclusions.
Paul
Fred :hatsoff:
