Several historical norms make a grain scale a valuable tool today. In numismatics, firearms ammunition, and medical literature references to the grain system are pervasive. For example, British and United States coinage has its basis in measurement by grains of weight and metal purity. European standards use grams, not grains.

    In ammunition and cartridge loading or reloading the literature still uses the traditional grain measurement. For example, in black powder days a cartridge could be designated .45-70-500, which referred to the caliber or diameter of the bullet in inches, 70 grains of powder --curiously sometimes a volume and sometimes a weight-- and 500 grains for the bullet weight.  There is nothing mysterious about grains. A 16 ounce pound contained 7000 grains. Division tells us that a standard ounce is equal to 437.5 grains. (I have used a reloading scale to weigh letters for years.)

     All historical literature and reloading data produced in the United States to this date continue to use grains for measurement for smokeless powder and bullets. For example, the standard lead projectile for the .38 Special had a traditional weight of about 158 grains. Bullets for black powder shooting are still weighed in grains. However, black powder is measured by volume designated in grains. If it applys to your needs, research this enough to understand what grain volume measure is.

     Coin collectors frequently weigh specimens. If compared to a traditional grain standard it is convenient to use grains. However, if European standards are used, grams and their decimal fractions are better suited.

     Old medical literature refers to grain measure as weight. However, the dram was also a useful measure but was both fluid (volume) and weight measure. Study the dram unit for its particular application to your interests. It will not mean the same to the shotgun student who reads about drams of powder as it will to the student of vintage apothecary measure in medicine.

     The basic understanding needed is that there are 7000 grains per pound and 437.5 grains per ounce. That much knowledge will tell you that a .69 caliber conical bullet used in the Civil War is a heavy lump of lead at around 700 grains. It would take nearly three .45 automatic bullets, nearly five .30-06 bullets of WW II, or more than a dozen M-16 bullets of the Vietnam period to weigh the same.

     This simple concept will help you understand a great many technical and historical measurements you may find from time to time. But you will still need milligrams when you go buy your Vitamin C.