Believe it or not, it is STILL POSSIBLE to do this kind of work w/o any power equipment at all-just picks and shovels!! It does take loanger, but as Napoleon said, "Where a man can stand, an Army can pass."

You can outline the back of the thing with railroad ties, nail heavy landscaping timbers across the "open' front end, (these hold in the fill & give you something to attach target frames to),then fill the space inside with dirt with shovels. OR, you can fill sandbags somepace for the outside walls,and bring them in on a 4X4 w/trailer.Either way, some manual labor is involved. But it's no big deal!

I built my own, it was 12'X12' deep 8' high, and had about 10 tons of dirt in it. When finished, I'm sure it would have stopped a 20mm aircraft cannon round....... (fired single-shot!!)

My first back stop was made of two by tens and measured 4ftx4ftx10in and was filled with sand. That much could be be hauled in buckets, and it stopped 175gr 7mm mag/ 30-06 armor percing and a load of 30-30 bullets. sand re-fills holes where logs get channel shot throught them and bullets in time can excape

I would use 4x4's with say 2 foot sand between them so it should be say 4'x4'x2' with an open top (6'x5'x3') even better etc. You need a safe back stop so even if it take some time to fill it its worth it. A horse feed bucket or a kids small plastic pool could be used to transport sand.

Stacked RR ties work well as a backstop too. 4 or 5 stacked on end is all you need. When one starts getting too shot up you can switch positions or just replace it.