The thought crossed my mind but I didn't want to waste an expensive self defense bullet on the test (9mm Hornady Critical Duty). The angle that I'd be shooting from also would put the bullet away from the diffuser. In all honesty, I doubt that a diffuser that was covered with more than 12" of water would get damaged by anything other than ball or FMJ ammo.
No shotgun?
No, I usually don't carry a shotgun when visiting clients places, but either the 9mm or .45 goes along for the ride. Concealed carry means that you aren't supposed to see it.
The angle that I'd be shooting from also would put the bullet away from the diffuser. In all honesty, I doubt that a diffuser that was covered with more than 12" of water would get damaged by anything other than ball or FMJ ammo. 
