This subject has become my recent obsession
With a pending trip to SD and weight concerns for hauling stuff around, I have been obsessed with this topic. With some effort I have found a pretty good solution.
I wanted a light rear shooting bag that was still stable so that, once you got it into shape it would not shift or require effort to keep it in place. If you ever read about the "My Pillow" guy Michael Lindell, one of the problems he faced (other than his enthusiasm for bucket-loads of cocaine) was that his pillows, filled with shredded foam, always seemed to lose shape. He solved that by using chunks of shredded foam of
three different sizes, combined in the right proportions. On a side note, his story is one of the craziest you'll ever read, and is actually very interesting
https://www.bloomberg.com/news/feat...terous-success-story-of-america-s-pillow-king (apologies for the bloomberg link). Spoiler: he beat his addiction and became a stand-up guy.
I thought that probably the drawback of a really light bag would be that it would not be as stable as those using other media such as sand or ground walnut shells, etc. I thought I could achieve the same thing Lindell had by using beads of varying sizes. That way I could have the lightweight of polystyrene but still achieve good stability. I don't know what the "right" proportions were so I pretty much used equal by volume among all three.
Here you can see the varying sizes with a quarter for scale
Mixed them together. The large beads were multicolored for extra fun.
Used a gallon ziplock to mix them together, and added powdered rosin to help even more with stability. There is a hole cut in the corner to help with getting the beads into the shooting bags.
I used two cylindrical-shaped bags by Tactical Tailor, one large and one small, that I bought unfilled. They have a simple velcro opening, and getting them sufficiently filled is a pain in the neck. I don't have pictures of that process but suffice to say I have not found an easy way to do this yet.
The result is the large bag weighing 6.5oz
and the small bag weighing 2.7oz
Compared to the weight of my old sand bag filled with actual sand which weighs 5lbs, 1.8oz
I was able to use these recently on my SD hunt, and was very happy with the results. The stability is great, as good as my actual sand bag. And you can't beat the weight, especially when your shooting bag already weighs a ton.
Here are links to the materials used
"Large" beads
https://www.amazon.com/dp/B0747QQNNP/ref=cm_sw_em_r_mt_dp_U_N2.cDbZEJ9ZTV
"Medium" beads
https://www.amazon.com/dp/B06ZZGT85J/ref=cm_sw_em_r_mt_dp_U_a3.cDbJ2B88MQ
"Small" beads
https://www.amazon.com/dp/B07B4YC8QQ/ref=cm_sw_em_r_mt_dp_U_n3.cDbQNMQN99
Powdered Rosin
https://www.amazon.com/dp/B00EM2WW12/ref=cm_sw_em_r_mt_dp_U_M3.cDbZTVM2MY
Rear rest bags, large and small
https://smile.amazon.com/dp/B07FVF89LG/ref=cm_sw_em_r_mt_dp_U_SfbdDbW9HVTE4