If I'm not shooting at gun club I shoot indoors too, I stand in my bedroom fire out of my bedroom through the hallway and into my little girls room where I put the traps.
I have a few homemade traps but the one I use mostly is made from wood etc, it's a solid wooden box type trap with a lead panel slightly angled back stop that is then wrapped in a two thick t-shirts, then the whole box is filled with pillow wadding, this stops basically 100% of rebounds the only time I might get one is when the trap has a few thousand BB's in it and is in need of a clean, the lid is made from a removable steel panel so after 2000+ shots/rounds I lift up the lid pull out the wadding and shake it into a black bag and most of the BB's come out, the wadding lasts about 30000 shots/rounds before it needs replacing.
It too is loud shooting in my house as the guns firing echoes, my trap and back stop is quite silent it's just the guns you hear, but I have a cool wife, she don't mind me having a shoot indoors.
You can see my trap in a few of my YouTube videos, after Christmas though I'm going to make a new one I have a good few ideas.
Happy shooting ATB Marc
Some of my favourite guns in. You collection, Umarex Beretta 92fs - Colt Custom 1911 - Walther Lever Action - TM Hi-Capa Custom Build Project - Colt SAA .45 & many more..