lots of guys prefer to use "SAND BAGS" for a rifle rest , these can be fabricated cheaply from old dungaree legs,
or bank coin bags if you have access to a sewing machine and you have minimal skills using it.
(yeah! ideally the wife or girl friend who may be more skilled with a sewing machine can help)

commercial sand bags, for rifle range use,
tend to be expensive and many people
buy them without realizing most are shipped empty.
most guys are reluctant to fill them with actual sand,
because its both heavy and it absorbs and holds moisture,

theres several sizes available
https://www.webstaurantstore.com/mm...MInavK9J-F2QIVyLfACh1q5gqvEAYYAyABEgKehfD_BwE
12" x 19"

https://www.ebay.com/itm/Canvas-Bla...in-Sack-Bags-6-5x9-5-Tie-String-/201031030561
6.5" x 9.5"
almost insuring that mildew/mold over time ruins the bags, or they can leak sand in your home, car, or storage area.
yes I'm well aware that many guys fill zip lock plastic bags,
then, double bag and insert the zip lock sand bags inside the canvas coin bags, to reduce the tendency,
some guys use uncooked rice
(this can attract vermin)
or packing peanuts
(too light and compress over time making the bags nearly useless)

the larger 12"/19" bank coin bags tend to work rather well

https://www.webstaurantstore.com/mm....yABEgKehfD_BwE


stuff the bank bags with rubber mulch filled zip lock bags with a 2.5 gallon zip lock bag filed with rubber mulch which is basically fine ground up old tires ,
and you have bags of the correct weight, firmness and these won,t attract vermin when stored,
get the correct fill percentage that allows the contents to be partly redistributed, the contents,
so you can manipulate the height/thickness and then fold the open end of the canvass coin bags and sew or staple shut.
https://www.homedepot.com/p/Vigoro-0...N8CB/203714941

i picked up empty shot bags at a flea market and filled some heavy plastic bags with sand and sealed them. i then put the plastic bags inside the shot bags and sewed them shut. the plastic bags keeps the sand dry and doesnt let the sand out to get on your rifle.

stuff the bank bags with rubber mulch filled zip lock bags with a 2.5 gallon zip lock bag filed with rubber mulch which is basically fine ground up old tires ,
and you have bags of the correct weight, firmness and these won,t attract vermin when stored,
get the correct fill percentage that allows the contents to be partly redistributed, the contents,
so you can manipulate the height/thickness and then fold the open end of the canvass coin bags and sew or staple shut.