Tuesday, October 18, 2011

Making Jacketed Bullets


In another section I went over how to make cast lead bullets. There is a limit to how fast these can go. That’s one of the reasons for jacketed bullets.

A modern bullet is normally two parts. There is a lead core to give it the mass and a copper jacket to hold it together before, and after, it hits. There are other types, but the copper jacket represents the bulk of the market. While far less common than casting lead bullets, there are people who make their own jacketed bullets.

For this, you will need a press and some ogive guides. That’s a funny word. Ogive. Ogive is the name for the curve at the tip of a bullet. A long, thin bullet with a gentle taper is has a shallow ogive, while a fat bullet with a sudden curve at the tip has a steep or sharp ogive.

The ogive helps determine how easily the bullet cuts through the air. It also affects the sectional density, mass, and terminal performance of the bullet. A steeper ogive means more mass per length of bullet, but it also means more drag as it flies through the air.

To make a jacketed bullet, you start with a lead core and a copper cup. The first step is to get the weight of the core about where you want it. The jackets can be bought cut to the right length of different types of bullet, so you have to take that weight into consideration as well. You also need to remember that as you put the ogive on the bullet, the lead will have less space to fill, and too much will mean the lead comes out the front.

Once we have the weights about right, we put a core into a cup, and run them through the press. The first die we use mashes the lead to fill the entire cup as much as possible. This is critical because any change in the uniformity of the lead will affect the center of gravity, which will cause the bullet to wobble in flight. This means it won’t stand much chance of hitting the target, and may actually disintegrate in the air.

With the core seated, we can begin to create the ogive. Here, we run it into the press until we get the shape we want. Some bullets have a large hollow point while others are nearly closed. Some have lead that goes all the way to the tip, others have a large volume of space between the lead and the tip. All of these affect how the bullet acts when it hits something.

The only option you really don’t have is a true full metal jacket. The reason for this is that the jacket we have is a cup. No matter what we do with it, it’s got to have an opening at the end. There is no way to seal it. Running it in from the other direction won’t do it. It just deforms the jacket and leaves exposed lead in the back of the bullet.

The final step is to size the bullet on the outside, and put a groove called a cannelure in it. This is sort of optional, but it does have some serious advantages. First, it acts as a belt to hold the jacket and core together. Second, it acts to limit how far the jacket can deform when it hits. Finally, it gives the casing something to crimp into when loaded. For some rounds, a little extra time is required to build up the proper pressure. Most large handguns and a lot of rifles use bullets with a cannelure groove.

Now, just as the shot cup can be loaded with other stuff in a shotgun, the copper cup can also be loaded with other stuff for a handgun or rifle. Silver powder for example. Fill the cup with a lead core, then drill out the center and fill it with silver powder. Place a small drop of wax in the top to hold it all in, and when the bullet hits, the bullet will slow before the silver it carries. The silver will be more or less injected into the target’s body.

A similar set up was used with mercury in The Day of the Jackal, the first one, not the remake.

Whatever you plan to add, be sure you have some way to make sure it’s all balanced as it spins, and that it can survive the incredible g-forces put on it when the gun fires. This is why a bullet made of ice won’t work. It’s too fragile and shatters the instant the gun goes off.

4 comments:

  1. This comment has been removed by the author.

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    1. Sorry, I didn't see this until today, and i can't seem to reply to a comment from my desktop.

      Corbin is one of the biggest names in this area.

      http://www.corbins.com/index.htm

      That link should be good place to start if you want to do it for real and not just write about it.

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  2. I have actually been casting fmj's in a mould and ramming through a sizer. First a made a steel bullet at .300 on my
    Lathe and now I melt copper tubing pour just enough in to fill 1/4 of the mould put my mould into a press I made that hold the steel in place like a jig of sorts and press with a hand press into the mould while its molten and after cooled I pull them out and melt the lead or filler I've used plastic anything softer and lower melting point than copper and pour into the jackets then throw on a glass check lube and run through the sizing die relube and bam the glass check is left on impact but the solid tip provides excellent penetration I've even used one of my steels with a 1/64 pin on it to make hollow point jackets for my 308 and hold a 1 moa at 400yds with a Mossberg and BTW don't buy a Mossberg unless you plan on making your own stock mag and replacing the barrel for tight groups

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  3. Gas check not glass stupid tablet with its spell check lol

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