Over 50 years ago, my Dad built me one in our basement. He tracked down a piece of steel plate, built a frame, filled the bottom with sand, and I shot BB as well as .22. The best part being, he shot with me. His only prior firearms interest or experience was WWII. Other than shooting with me, he never shot again. About the same time, he was concerned that his WWII issued 1911 was a potential danger, and gave it to the local PD.
Although he was not a gun guy, he was always there to encourage me in endeavors where time was well spent. My interest led me to Junior Rifle, modest competitive shooting, a lifelong interest in small arms, and a professional career touching all or part of 4 decades, where I was issued the finest sidearms and rifles the U.S. Gov. had available.
I retired in 2001, just before 911. Years before, I had been issued a scoped Win. Mod. 70 .30-06, built in 1957. When the younger guys came along, they were hot to get the new synthetic stocked, tweeked and geeked, .308, I hung onto that pre64 mod. 70. I hung on to that great rifle until my exit interview the day I retired. They had to pry my fingers of the rifle just before they threw me out the door.
A thread on indoor ranges??? Yes, it caught my eye. Enjoy.