"Whole-Wit" hhdh9uhh@fsb wrote in
:

Imagine 22,000 lbs of ground-up tires with all the steel and other
crap removed, ground to @ 1/8" pebbles. This is the material in the
backstop of a shooting range. There is a conservative estimate of
10,000 lbs of lead and copper to a much lesser degree in the rubber.
This isn't the first clean-out/rebuild, the last one was five years
ago. The idea is to remove all the material, separate it and reuse
the rubber. One of the ideas we've had is to float the rubber in water
and skim it off. But, 1/2 of a sample amount floats, 1/3 sinks and
1/6 stays suspended. In a 1/3 cup of the material, there was 64 grams
of lead! I doubt that there is much lead in the material above the
target line. The sample was taken at the very bottom, about 5' below
the target line. They don't really want the range down for more than
a week to do the clean-out and replace the front which is 4' wide x
3/4" thick conveyor belt lengths suspended from the ceiling and
anchored to the floor and overlap by 8" and screwed together. The
conveyor belting is bulging out close to a foot in the center of each
of the ten lanes. It seems that this type of backstop is excellent
for stopping bullets and keeping the dust to a minimum.

Some of the vendors of this sort of range have auger systems to separate
the lead. My club just installed a new backstop with the auger system
included, but I haven't seen it, so I have no idea how it works. My
understanding is that you can get the backstop without the auger, and
then hire the backstop company to come & periodically clean the lead out.
Another club in my area has a pulverized rubber backstop, and they have
some means of cleaning it, but I don't think they have an auger system.

If you got the pulverized rubber from a commercial backstop vendor, I
would hope they have a means of getting the lead out.

Doug White