You also need an outside vent away from you and a fresh air source behind you and a fan to move the exhaust in the right direction. Sound proofing panels overhead to dampen the sound and if you have exposed wiring or plumbing you need to protect them. Ain't no such thing as an accident free range where a bullet never goes wandering in a direction you didn't mean for it to go. Hitting a copper water line or breaker panel or washing machine does wonders for your morale and pocket book.
I had a 24' range set up for my kids and a Wooden 2x4 cage they had to shoot through limiting their range of motion with the barrel and I loaded the gun and handed it to them for each shot. My exhaust system was going the wrong way but was the best I could do. I would not do it today unless I could do it right but in 1976 I was younger and poorer and hadn't thought all of these things out. Wasn't a problem because I had access to an outdoor range a mile from the house and most of their indoor shooting was with a BB gun at a 22 caliber rated bullet trap.
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.