Very nice, I did penetration testing with rubber mulch a while back. Impact .25 at 3 feet. Deepest penetration was around 6 inches. At 10 yards, should be good, but do watch and make sure you don't drill a hole through the mulch. Normally it'll break up and self pack down, but eventually you could drill a hole and penetrate. Give the side of the target a good hit once in a while to make sure the mulch continues to settle and stay tightly packed.
Sorry, can't spell today. Need sleep!