He's a better idea:
Use rubber crumbs contained within sheets of rubber conveyor belt material. It's what our indoor club range uses. A few feet in depth worth of tire crumbs will stop a .30-06, nevermind any handgun rounds. In addition, the crumbs capture the spent bullets, making it easy to recover them, either for melting down and re-casting, or for sale as scrap.
An even better advantage on an indoor range is that lead levels drop dramatically, since there's no vaporization when the bullets pierce the sheets and hit the crumb.
Maintenance is easy. Just patch holes in the sheets using pre-cut convery sheet patches and drywall screws. When we clean the range once every year or two, we use a large propane powered vacuum cleaner to suck out the rubber. Then we sieve it for the bullets and blow it back.