Each bullet is measured in Dia of the bullet and in the weight of the bullet. The bullet weight is measured in grains. As stated there are 7000garins to a lb. So for example if you had just the bullets in your hand,the bullets now not the loaded shell--- If you had a lb of 150 gr bullets you would have 46.66 bullets in your hand. Dia. of the bullets is just that ,what it measures out to be. The 30 cal bullet measures out to .3085 or .308.ect. If your interested in knowing about bullets buy the book Cartridges of the Worl by Frank Barnes. It will keep you busy forsome time. Hope i helped vangunsmith