Re: shooting bags
Also, hard to get, but since I race motorcycles I have Tire Balls. They are not exactly round, semi round, can be inflated and deflated with a basket ball pump. Put that inside a small caldwell bag with ears or put it in a sock. Light weight.
I like water wings for back packing. Deflate and they take up little room. Inflate in seconds and you have a rear rest. It's not as tight as sand, but once you settle in it works way better than nothing.