LEAD HARDNESS

Cast bullet shooters always get interested in how hard their bullets are, no matter if they cast the bullets themselves or if they purchase them.  Producers of cast bullets  have picked up on this and go out of their way to make sure the prospective buyer knows that their bullets are "hard cast", some going so far as to include other metals in the bullet alloy so as to have something unique.

How hard does a bullet have to be?  I had some alloy once that went off the scale of my BHN Hardness Tester.  BHN stands for Brinell Hardness Numbers.   One reason I like BHN (as opposed to other ways of measuring hardness) is that the numbers are relational.  That is, a bullet of 10 BHN is almost exactly twice as hard as a bullet of 5 BHN.  Not all forms of hardness measuring does this.   Technically there may be "more accurate" methods of measurement, but for shooting purposes BHN does just fine.

Anyhow, this lead I had went off the scale.  I had a bar of it about 20" long, 4" wide and 1" thick.  When you held it up and whacked it with a hammer it would ring it was so hard.  And it made lousy bullets.  They were HARD but they were not TOUGH.  When you fired a bullet of this material into a log or a 4x4 fence post the bullet would break up.  It was hard to the point of brittleness.

A bullet needs to be tough enough that you do not over-run it's ability to stay together at whatever velocity it is reaching it's target.  It needs to be soft enough that it "upsets" and seals the bore, not allowing any gas to escape past it. Bullets that are too hard will lead a bore as quickly as bullets that are too soft.

The hard bullet that does not "upset" (obturate) does not seal the bore as it is going through it. It allows gas to escape past it, causing gas cutting on the bullet base and ultimately leading the bore.  A bullet that is too soft will not "take" the rifling (if driven too fast) and will gas cut also and will thus lead the bore as well. Soft bullets can also lead the bore through other mechanisms, especially if the lube is not adequate. The ideal hardness depends on the velocity you are driving the bullet at.  For target loads like those used in the .38 Special wadcutter, pure lead or nearly so works just fine.   Velocities are normally under 800 fps for these loads.  Many "Cowboy:" loads fit in this category. For high-velocity loads the bullet must be harder than "pure" lead.   Hunting bullets must be of adequate hardness to retain their integrity as they drill through bone and muscle, sometime quite a few inches of it.

What little experience I have had shooting game has made me conclude that water-quenched wheelweight alloy works just fine in the .357 Magnum, .41, .and .44 Magnum, the .45 Colt, the .454 Casull and the .475 Linebaugh.   Those are the calibers I have tried it in. I have shot game with each of thosecalibers. Based on what I have seen I believe I can say it will work well in the .500 Linebaugh and about any other sixgun you want to run it in.  A hardness of 15 to 18 BHN is tough enough that the bullet holds together and elastic enough that it obturates and seals the bore.

Now if I were going after big bears or other large dangerous game, I would opt for bullets of 22 to 24 BHN.  These will hold together a bit better in long, deep penetrating shots.  However, for the use I normally put them to, the water-quenched bullets work just fine.

HOW?

Water-quenching is simple.  Just drop the hot bullets directly from a HOT mould into a bucket of water.  The mould and bullet should be hot enough that the bullet "sizzles" a bit when it hits the water. I use a 6 gallon bucket and I have placed small pieces of styrofoam on the top of the water to keep splashback to a minimum.  You do not want water getting into the mould.  If you do get water in the mould, dry it out before casting! You can have a lead explosion easily when you go to pour the next bullet if you have water in a cavity.  Serious injury can result.  Take heed.   Usually all you have to do is wait for a minute or two if you are running the mould really hot.  The heat of the mould body will dry out the moisture, given a chance.

When you are done casting take the bullets out of the water, place them on a towel and let them dry. Once they are dry I size and lubricate them, then put them away. They will reach their full hardness in about a week..

The "cool cast" bullets were cast from a "cool" mould (basically a normal temperature mould) and dropped into water.  If you do not run the mould HOT it is no more effective than casting them normally and allowing them to air cool. The "air-cooled" bullets were cast from a normal temperture mould and dropped on a towel to cool in the air.  The "hot cast" bullets were cast from a hot mould and dropped into water.

Bullets will lose their hardness over time. A heat-treated bullet of 34 to 38 BHN will "soften" to around the hardness of linotype in about 2 years - IF - it has not been subjected to heat extremes.  Keep your bullets in a cool place and their hardness will last longer.  If you really want to keep bullets at their maximum hardness for a long period of time, store them in your freezer!  Momma may have something to say about you putting 50 pounds of your favorite bullet in with the chicken and hamburger, but you will have to work that out.  CAUTION:  If you do store them in the freezer, be sure to let them warm to room temperature BEFORE you load them.   Otherwise you run the risk of moisture condensing on the bullet base INSIDE the cartridge.  Not good.

I have heat-treated wheelweight alloy successfully over the years.   You can make it quite a bit harder than linotype, but I finally asked myself, "Why?"  For what I need that range of hardness is not an issue.   Water-cooled bullets from a hot mould can be driven to quite high velocities and they work well.  I have not heat-treated any bullets in over 14 years. 

All this is making the assumption that you have the proper lube on the bullets.  If you do not, even the best bullet at the ideal hardness can lead the bore.  That is another story and will be told in the future - hopefully.

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