Are trap guns not usually single-shot or double-barreled anyway? This would seem to be a moot point. Those are good rules. Why not simply unload your carry gun out in the parking lot or something before going in? Except for disallowing steel-cored or -jacketed bullets (is this what you mean by FMJ?) due to backstop damage, the indoor range I go to has none of these rules. In fact, with a certification by an instructor (one-time $15 fee) you can draw from the holster. And they rent machine guns, so they can't very well ban rapid fire. But the conditions at your range(s) might be different.