A bag of sand from a home improvement store is cheap, heavy and therefore stable. It will just be too large. Some type of smaller canvas bag, like a bag of junk silver comes in (a bank bag or even the bag shotgun shot for relaoders comes in) works best and cheapest for me. I stack two 10# bags on top of each other to support my fore-end (not barrel) and then one smaller 5# bag for under the rear of the stock.

Snuggle the gun into the soft sandbags. Get the gun positioned so when you let go your crosshairs are right on target (each shot). Then apply yourself to the gun without moving (muscling) it, and let it show you how accurate IT is. You just hold on and mush the trigger without moving the gun. Follow through.

You are correct that your ACOG is not primo for precise accuracy, but it is a good, rugged, fast acquistion optic that should do just what you have specified. It’s always nice to find the maximum accuracy and load for any gun. It builds your confidence. Then set it up more to meet your needs.

IOW, borrow a good 10x scope, get the gun doped on sand bags with it to know it’s maximum accuracy potential. Then mount your ACOG and bipod (Atlas is a very good one) again and go to work.