Hi Guys!
Howdy, and welcome!
I tested today to see what penetration to expect from the hredded rubber used as a back stop for my garage range. Using a cat litter plastic bucket 14 inches deep, I placed paper markers at the 4 and 8 inch depths as I filled the bucket with shredded rubber chips ... not nuggets, shreds. Atop the rubber I placed a Cheaper Than Dirt (gougers that the are now) catalog then the plastic bag emptied of rubber bits.
At ten feet I fired a CCI Stinger, then a 22 Winchester dynapoint magnum, then a 73 grain 32 acp, then a 124 ball 9mm into the rubber filled bucket. The .22 rounds made it past the 4 inch paper but disintegrated before reaching 8 inches. The 32 acp Fiocchi made it just past the 8 inch paper and was found in tact, while the 9mm ball made it to 12 inches and had a slight deformation where it hit perhaps one of the .22 rounds or the 32 acp jacketed round.
I'm going to build my backstop 4' x 5' x 18 inches deep, on a casters frame so it can be rolled out of the way when not in use. The frame will raise the stopper18 inches off the garage floor and there will be a panel in the end that will allow higher caliber rounds to be test fired into the long-way shredded rubber. The face of the stop will not be shot unless there's a flier when shooting at the 12" x 12" x 12" steel bullet trap in front of the stop.
Thought folks might like to know what kind of performance to expect from the shredded rubber bullet trapping system.