You cannot practically bullet proof against rifle rounds. I've seen .223 blow holes through 1/4 inch steel. It's not going to be terribly dangerous after expending all that energy and being deformed, maybe even destroyed, but it points out that you can't do it on a large scale. You can't use kevlar wallpaper.
The ceramic plates and vests used professionally work about as well as they can against rifle rounds.
On a structure, all you can do is build the thing solidly and the energy will be absorbed. Cast concrete will do it, but almost anything can blast through a cinder block and cause injury or death. A foot or two of compressed dirt. Two inches or so of shredded tires. The Earth ship that the hippies make? Dirt pounded into old tires that are stacked to make a hovel? Sure, 2 feet of dirt will stop a bullet, and the last layer of tire will help even more.
The ceramic plates and vests used professionally work about as well as they can against rifle rounds.
On a structure, all you can do is build the thing solidly and the energy will be absorbed. Cast concrete will do it, but almost anything can blast through a cinder block and cause injury or death. A foot or two of compressed dirt. Two inches or so of shredded tires. The Earth ship that the hippies make? Dirt pounded into old tires that are stacked to make a hovel? Sure, 2 feet of dirt will stop a bullet, and the last layer of tire will help even more.