The specific gravity of bullet alloy, or any other solid, is easily done. A scale/beam balance, some water, a cup, thread and a sample will do it. The pictures won't work; for a copy, ask joeb33050@yahoo.com BULLET ALLOY SPECIFIC GRAVITY Cast bullet shooters are sometimes interested in the composition and hardness of bullet alloys. Precise assays of these alloys are expensive, and individual shooters seldom want to know enough to pay for the test. Hardness of bullet alloys can be measured with hardness testers that are available from LBT, Saeco and Lee. I don't have a hardness tester, and have used the Specific Gravity of alloys to estimate the composition and hardness of those alloys. This isn't precise, but it's close enough for me. My records of weights of 311299 bullets shows the weight varying from an average of 208.8 grains (wheelweights) down to 197.8 grains (wheelweights with foundry type added). This is a difference of about 5% in weight and specific gravity, and this difference of 5% is a great difference in percentage of tin or antimony and in hardness. Keeping track of weights of bullets in different alloys is one way to estimate the hardness of the alloy. Measuring the specific gravity is another. The Specific Gravity of a material is the ratio of that material's density to the density of water. If a quart of material K weighs twice as much as a quart of water, the Specific Gravity of material K is 2. If a cubic inch of metal L weighs eleven times as much as a cubic inch of water, the Specific Gravity of metal L is 11. For lead-tin-antimony alloys, as the specific gravity goes down the hardness goes up. If there are other metals such as gold or silver or zinc or arsenic or cadmium or copper, we'll never know by calculating the Specific Gravity; but if it casts good bullets it probably doesn't have much of anything exotic in the alloy. Specific Gravity Weight of sample (bullet) in air minus Weight of sample in water equals Weight of the water displaced by the sample Weight of sample (bullet) in air divided by Weight of the water displaced by the sample equals Specific Gravity of the sample To measure the Specific gravity of an alloy we need a sample of the alloy-a bullet works fine, a scale, a glass, some water and a piece of thread. Here's the scale up in the air with a bullet suspended by a thread from the pan holder. Just hanging there. The bullet with thread weighs 434.5 grains. Here's the bullet in a glass of water, not touching the sides or bottom of the glass. Just hanging there. The bullet and thread weigh 395.6 grains in the water. We can safely forget the weight and volume of the thread. Weight of sample (bullet) in air 434.5 grains minus Weight of sample in water 395.6 grains equals Weight of the water displaced by the sample 38.9 grains (Eureka!) Weight of sample (bullet) in air 434.5 grains divided by Weight of the water displaced by the sample 38.9 grains equals Specific Gravity of the sample 11.17
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