Sand Type for Range Backstop

'Have had just about everything mentioned above (vegetated soil) for ~40 yrs on an old fam farm. The state public ranges are made of sand, so that they may periodically do a cleanup of heavy metals in the soils from 1,000s of shooters over the year. The sand berms are huge, requiring much more material than a personal range made of more densely compacted soil . The angle of repose for most gravels and sand is 45 degrees. After that, it's going to wash and slough away. Soil can be compacted and vegetated (at a much steeper angle too, once shot into.) All that said, I like the idea of the heavy, 1" thick rubber mats hanging vertically in succession. There's a 100 yd indoor range and several other public outdoor ranges featuring that. The bullets can be pulled out of the mats or collected in a trough beneath it! One indoor range has a several feet thick, recycled tire blocks that stops everything excepting the big bore solids. Although I haven't made one yet (out of hanging rubber mats,) I eventually will (it's a fine backstop that additionally holds targets!) I've seen people hang the 1" inside of poly 55-gal drums (which additionally serve to slow bullets down and holes "heal" upon being shot.) Depending upon the size of the rubber used (full-size truck bed or livestock mats hung in succession will stop bullets,) but I'd simply keep the soil backstop in-place as an added measure of security. 'Also have a red (repurposed ATV/UTV) flag that gets put up at the 300 yd backstop along the property boundary, when shooting. Actually recently looked at aerial photos with a logger to create a 650-850 yd range that both hunters and wildlife will profit from! (essentially cutting down one area of tertiary-now forested, previously pasture land surrounded by big woods, but leaving the high grass, brush, berry bushes up-it's in a low spot and the 650-850 target backers would be at higher elevation-same as the shooting position.) There are many basic range designs available online...Good luck! These days, I think the soil is (exceedingly compacted/vegetated) only 6' wide at the bottom and about 4' thick at the top and about 6' high. Plenty for only 300 yds. People should be dialed in appropriately at 100 prior to taking longer shots! I give the neighbors a test at 100 prior to proceeding farther out...