A little while back I posted about a simple bullet trap I copied from a plan on an online forum. It is just a pressure treated plywood box with a hinged lid on cart wheels (14" x 14" x 24") filled with rubber playground mulch.
I recovered about a hundred spent round balls from it, all looking roughly hemispherical. I wondered how much lead had been abraded from them on their way through the front face of the box and the rubber mulch.
I finally got around to weighing them - 10 at once on a precise (.002 lb) scale in the herbs and spices department of my local food co-op. (In a paper packet to avoid contamination)
They weighed in at .258 lb, which works out to 1806 grains, or 180.6 per bullet. The original weight of the Hornady .495 balls was supposed to be 182 grains. That's 99.23% of their original weight, probably within specification.
Nice to know that I'm recovering virtually all of my lead, and not depositing loads of powdered lead in the box. I recommend the simple box trap to frugal shooters.
Let's see - if I average 20 shots a week and lose 1% of ball weight per shot (figuring in casting losses), then I lose one round ball equivalent every five weeks. A box of 100 should last 500 weeks, so in about 9 years and 7 months I'd be down to my last bullet. Hmmm...there has to be a catch.
Canute