Originally Posted by
curioushooter
I did a number of tests on properly calibrated (resistance match to pork loin and deer leg which are the same) gelatin. Water and other mediums (clay, mud, newspapers), except perhaps that synthetic gel, should be ignored. I did tests using water and not only is it useless for determining penetration (which is at least as important as expansion), it tends to exaggerate expansive properties of hollowpoints and diminish it with solids.
My findings were stunningly consistent. They could follow formula. And I suspect that millitaries throughout the world figured this out a long time ago.
Regarding handguns with solid cast bullets. No real expansion is observed at all until you are going somewhat above 1200 FPS impact velocity. You will observe deformation, but this isn't the same as the "mushrooming effect". Once you crank it up to 1400 or greater you start to observe effective expansion in solids. How many handguns have an impact velocity of 1400 FPS? I found 1100 FPS to be about a break point. Interestingly this is about the speed of sound in air at normal elevations.
With hollowpoints you observe consistent expansion down to about 750 FPS impact velocity or so. I like 800 FPS or more with a SOFT alloy containing no antimony, only tin. The problem is that at such low velocity there really isn't an abundance of momentum to carry that expanded bullet very deep. The classic 38 SPL+P loaded with a 158 grain or so soft SWCHP out of a 1 7/8" snubbie gets just under a foot of penetration, usually 9-10" with a 4 layer denim cover. This was recognized as an effective load because it is. No more effective non-jacketed load I have found for a snub nose 38. It basically defines cast hollow point performance at the bottom end of the performance envelope. Out a 4" revolver this load improves owning to the almost 100 FPS it can pick up, getting it to penetrate over a foot and still holding together.
Really soft hollow points fragment if you push them too hard. 850-900 FPS you will start to see fragging, not on every one usually, but sometimes "tearing". Like one of six or so. At 357 mag velocity you will frag unless the alloy is toughened up with more tin and copper. 16:1 works, so does an alloy I call 96-2-2. Which has equal by wight parts antimony and tin (together added at once ounce per pound), is harder than 16:1, and is cheaper as it has half as much tin. Once you are up to 3% antimony it seems to "crystallize" the alloy greatly increasing brittleness and will cause fragmentation to a significant degree. Wheel weights, especially older ones, seem to have too much antimony. Tin, if you can get some, is your friend.
One of epiphanies I had regarding cast hollowpoints is that they act like a little parachute. If you get expansion, you will reduce penetration, in almost a linear fashion I suspect. Penetration can be improved by lengthening the bullet (adding mass) or by increasing velocity (but this also may increase penetration or cause fragmentation which results in loss of mass and reduction of penetration). The straightforward way is to increase mass. This is why 38 SPL+P beats 9mm with cast bullets IMO.
Predicting the performance of hollowpints is not trivial. All my testing was done almost perfectly perpendicular to the gel block. The few tests I did at angles revealed that really big cast hollow point cavities with thin walls like to collapse rather than expand, sometimes you get a half expanded bullet or something (this is sadly true of that 38 SWCHP). It seriously eroded by "trust" in them. I found that jacketed hollowpoints are quite a different animal too. The much tougher jacket allows the use of very soft lead alloys for the core and it arrests expansion, prevents fragmentation, allowing the manufacturer to really dial in the performance profile. Of all the jacketed bullets I tested I have have some favorites. I even did "barrier" testing shooting plywood and my wife's cookie sheets. The Federal 130 grain HST bullet in their 38+P defensive loads is the last word in snub gun loads as far as I am concerned, though it is annoyingly difficult to use with a speedloader. And the Hornady 158 grain XTPHP in 357 full sized (4" barrel or longer) revolvers and the 180 grain XTPHP in 357 rifles. 147 grain XTPHP in 9mm loaded hot.
Compared to solids it is a chore. This is one of the reasons why I made a paradigm shift to using big bore cast solids instead of medium bore cast hollowpoints for handgun hunting (though I confess I still have a fondness for 357 Max with 180 grain Hornady XTPHP). Big bore solids are stupidly predictable (the make a hole of crushed tissues at least as big as the diameter and usually perforate normal sized animals at any angle). So it leaves more time/energy to focus on achieving accuracy and consistency. For me big bore starts at about .43".
Posting Permissions
Reply With Quote
