As of this weekend, I have about 10K rounds down range. Tore the chip wood from the front of the backstop to check on the rubber mulch and it is working just as I planned for it to. Where the center of the targets have been shot multiple times, the rubber crumbs and "shavings" as they called them have settled and packed so the more you shoot in one place, the more it repairs itself and becomes more resistant to penetration. I will run another 10K to 20K rounds over the next two to three weeks and make certain it is still doing the same thing before I let anyone else on my range. I do appreciate the comments and took them in a positive manner. However, if you have never constructed one from scratch, you really do not know what you are talking about because it is so much different using the mulch and crumbs than anything else I have ever been exposed to and have been shooting and building my own ranges for over forty-five years. I will be the first to say if it fails so anyone else wanting to use the rubber crumbs will be aware of the shortcomings if any. I have not seen any yet but I want 75K to 100K down range before I say it is a really good thing!
NRA Endowment Life Member - TX Concealed Handgun Instructor
Experience - What you get when you don't get what you wanted!