Close , way back when an indoor range used to be a steel plate backstop set at an angle to direct any impacts either up or down . There was no real standard for the steel and use of 1/2 inch mild steel sheets was common and fine for pistol usage . However as time went on they got used with either light rifle ammo or slugs from shotguns and either can and will leave a crater or dimple in the steel . Now the backplate handles that just fine , however the deformations that " over caliber " useages creates causes an irregular surface . So rather than operating as designed to safely channel rounds to a safe direction untill spent in sand or other media the backstop now is luck of the draw on angles . You can verify this by the simple measure of before the range is open or after it closes walk down and feel the backstop , it wont feel smooth rather you will feel a series of pits in it . Hitting the lip of a pit is what can and does make the " back splash " where you may get hit or cut by particles . I will note that while it is scary and unpleasant to get cut by a bullet remnant it as a rule is not life threatening, The frags hitting you simply dont have enough energy do do much more than a simple skin cut as long as you have eye protection . This is not to excuse ranges that have improper backstops , or old pitted backstops , it is just to state facts of indoor ranges . When i qualified as a firearms instructor for my dept i shot at the indoor csp range . One of the courses of fire involved 50 rounds of 12 ga slugs , during this about half a slug whacked me on the knee hard enough to cut my pants and make me say words i shouldnt have . I was not long term hurt , however at that point i recognised that maby the csp response team should maby shoot in the snow rather than co opt the main indoor range for the agency lol .
Whatever they are using for a backstop is not working it sounds like it is leaded up and you are basically shooting into lead and getting ricochets,even outdoor ranges over time will dig up the dirt in the berm backstop and remove the lead by screening it then put the dirt back