Maximum Expansion with BT Sniper Die Bullets
After a long delay, I think I have new information useful to all of you...along with pictures to prove it. BUT I am still having trouble with that, and am not likely to match BT Sniper's photography skills anytime soon.
Initially, months ago, I had nothing but trouble getting expansion with the .40 boolits made with 9mm case jackets. Even at 10mm velocities, they did not expand, although penetrating nearly 8" of solid wood. Sorry guys, I did not and do not buy the argument that it happened because I was not shooting into ballistic gelatin or liquid or soft earth. That was not the problem. I've been reloading and making bullets for 50 years. But at first, I was not hollow pointing them, and that did contribute to the problem.
There is nothing wrong with Brian's fine dies or boolit design. The limitation is using unmodified 9mm empty cases for jackets, but I think I have it worked out.
First, let's understand that this is a brass alloy specifically designed to contain high pressure as well as possible. But for our purposes we want the opposite. We need to have the jacket allow the inner core to expand, to dissipate energy over a broader area. A high strength jacket will not permit that.
Commercial defensive and hunting boolits are made with a soft copper jacket, which allows the core to expand dramatically more easily. Our homemade jackets virtually prevent that...no matter how much you score the jacket around the nose. They work like girdles, holding the lead in. The commercial guys even taper their wall thickiness, to make it progressively more thin toward the nose. That's how you get those beautiful mushrooms from Remington's Core-Lokt boolits.
True, we anneal our case jackets to make them more pliable during the forming process, but that is not nearly enough. The only reason we need the jackets at all is to get better velocity without bore leading, especially in unusual types of bores, like the Glock family of polygon bored barrels. So what we really want is a jacket only long enough to cover the bore riding surface of the boolit, and we could even get along with less than that.
So all of this started out partly as theory. Now I'm confident it is fact. To prove that, I made three types of .40 boolits, all weighing 180 grains ahead of 5.5 grains of Bullseye, a maximum load for .40 S&W. The test weapon was my Glock 27 with 3.5" barrel.
The only variable was the length of jacket and amount of pure lead left uncontained by jacket wall. First, I used untrimmed 9mm cases, where the jacket wall continues all the way to the flat on the nose of the hollow point boolit. Then I made boolits where the jacket covers only half of the rounded boolit ogive. Last I made boolits where the entire ogive is exposed soft, pure, deeply hollow pointed lead. Let there be no doubt, that is the only one you want for defensive use!
So below is a picture of what happens (or does not happen) with jackets left the full length of a 9mm case. We're looking down on one unfired boolit's hollow point, a loaded round, and two boolits that have passed through a 1.5" thick seasoned hard oak board, lodging in a pine board behind. Incidentally, all rounds fired in this test went through the same long board. And coming out the back, they made quite a mess of it.
http://i1231.photobucket.com/albums/.../MaxJacket.jpg
Next we have some fired and unfired boolits made with the jackets trimmed so they cover only 1/2 of the ogive. You can see quite an improvement in expansion, fired through the same board at point blank range. But it still was not what I wanted.
http://i1231.photobucket.com/albums/.../MedJacket.jpg
Now for the good part. I made boolits with case jackets trimmed to cover only the bore riding part of the boolit. It got me exactly what I wanted, maximum and reliable expansion at point blank range from a short barreled pistol. Notice how the pressure sets the fired primer inward. You should see the looks on the faces of some guys seeing this boolit for the first time, as it looks like a stubby loaded round.
http://i1231.photobucket.com/albums/...imumJacket.jpg
So how do you shorten cases for jackets? I recommend you do it before annealing, as hard brass is easier to cut without the cutter digging in. And you can tighten it in a chuck more firmly without crushing it. But it need not be tighter than just enough to keep it from turning in the chuck. I use an old Sears/Atlas 6" bench top lathe. You could spin your cases in a drill press, mounted hand drill, anything. Or use some kind of cutting saw. But be sure you have some sort of "stop" arrangement to keep the cuttoff length consistent. Here's how I did it. In a few minutes, I made a little adjustable guide to clamp on a lathe cutter I also made. The lower screw holds the guide to the cutter and the upper screw (both with lock nuts and both threaded into the guide) regulates length cut. In the end, I stopped using the screw at all, as the length cut with the case mouth touching the guide body gave me the maximum cut I wanted...all of the ogive area. So...
Here I was set up to take off only about 1/16" of case mouth. That gave me the second type of expansion, medium, but not quite what I wanted.
http://i1231.photobucket.com/albums/...ingLongest.jpg
Here is the adjustment screw backed out all the way, to trim the jacket so none of it holds in the rounded ogive lead of the boolit. Set lathe RPM to a medium speed and the cut takes under 2 seconds.
http://i1231.photobucket.com/albums/...tShortest2.jpg
Here it is with the lathe running the the jacket touched by the cutter.
http://i1231.photobucket.com/albums/...tShortest1.jpg
...and then the piece falls harmlessly away or hangs on the cutter. You can do about three per minute if you are fast with the chuck key.
http://i1231.photobucket.com/albums/...stFinished.jpg
Here are a few of these last type of boolits, all fired through the same 1.5" hard oak board.
http://i1231.photobucket.com/albums/...ts/MinJkt4.jpg
http://i1231.photobucket.com/albums/...ts/MinJkt3.jpg
http://i1231.photobucket.com/albums/...ts/MinJkt2.jpg
So the moral of the story is, keep the jacket as short as possible, unless you want deeper penetration in big game or something. For low velocity handguns, I think this is the only way to go. Stick with a pure lead core and a big, deep hollow point. These should all feed flawlessly in just about any modern semiauto handgun. You have enough exposed jacket, and at the right place, to assure that.
These cores were all simply 120 grain truncated cone pure lead 9mm boolits, placed nose down in the slightly belled short jacket and seated with my core seating die. I strongly recommend you use Brian's core seating die or the equivalent. It makes a much better, uniform boolit and is easier on your boolit forming die.
Is this a lot of work? Not really. You can whistle through 50 or 100 of these in no time. But I don't shoot them at tin cans or paper targets. They are "for serious". And now I am confident they will work. For the few I make, annealing cases on a coat hanger wire over a propane torch flame takes 20 seconds per case. What more could I ask for?
And by all means have fun.