A lot of indoor ranges were designed to handle mostly handguns or rimfire rifles. I wonder if the range that the op visited would allow a person to shoot a 30-30 deer rifle? Instead of the shop owner insulting the op's choice of weapon, he could have just told him that his backstop wasn't designed to handle fmj military rifle ammo. There's a range about a half hour from my house where they only let you shoot ammo that you buy from his store, we don't go there any more. Another place that's just ten minutes away lets me shoot my reloads, they only are designed as a pistol range but I download plinking rounds for my 30-30 and they let me do it as long as I'm getting pistol velocities from the rifle. They said that the backstop can handle it, but the noise level from full power rifle loads that are fired indoors is quite loud.