It was interesting to me when I started looking up how things are actually designed - or recommended by sources for how to be designed. The pile of dirt berm is actually supposed to have an overhang parallel to the earth that extends from the back of the berm past the start of the berm where it turns into an incline in some sources I've read. That cover has some specs for thickness and material to stop rounds based on caliber. Baffles are interesting because basically, if you have a fixed shooting position, say in a 50 foot pistol range - this is what I was thinking of doing, you really need something like 3 baffles between the shooter and the backstop. In this case - think of the baffle as being like a wall with a door or window in the middle, so - from the shooting position, if you bounce a round it hits a baffle, if you are shooting a revolver single action and cock the pistol, and it has a light trigger - and fire early and launch a round at 15 or 30 degree angle up in the air, you hit a baffle - same with something that would go to the side, so - basically this would be planning for the worst cases. If the shooter was in a covered enclosure, also designed to contain rounds - you'd be covering all your bases - even if someone fired directly vertical by accident - go to an indoor range and look up when in one of the booths, it happens - you'd just hit a ceiling designed to contain rounds. My quick ballpark estimate was something like this would be between 5 an 7K to actually build out correctly - maybe a little more, but where I am - houses 400-600 feet all around, can't see doing less if there was going to be regular periodic shooting, especially with guests and friends/family etc. The thickness of the baffles is based on caliber used - higher caliber, thicker baffles, more money to construct. I will probably never do this, because I can drive 15 minutes and there is a local pistol range, and for the expense I could buy everyone I know who shoots a lifetime membership there.