Ive seen a 55 gallon drum set on legs in front of a bench. The hole through the center was a good 8 inches, plenty to see through. The drum had five plywood baffles and foam glued and stapled all over. It worked really well to mitigate noise. Can do anything about sonic crack. If anything needed to be changed the lid just clamped on so you can get inside easy enough. I'm on both sides here. I like to have and be a good neighbor. I shoot mostly canned because I just like to have them on. It's not always possible, especially when I'm testing bullets that may be marginally stable or the rifle isnt set up for a suppressor. My saving grace is i have land and access to more. I did have a terrible neighbor before who thought he owned my place. We had some run ins. One day he called telling me no shooting allowed, lol. Then he said I couldn't ride my four wheelers down my fence line because it was, get this, "beyond his comfort level". After that I never shot with a can on and I rode my loudest bike up and down the fence at will. I even thought about putting a kennel up and buying a few hounds for next to his line.