This thread is from just a couple of days ago and may give you some ideas.
What shooting rest bags?
I'll reiterate what I said there though because favorite doesn't necessarily mean best.
I prefer a 9-13" Harris bipod and the rear bag from this website's gear shop. I've used an old wool sock with rice and/or beads in it too but I like the rectangular bag better so far. It's just more versatile and easier to tote around IMO. I'm still on the hunt for something that beats this for stability, versatility, and toting around. But I'm not very optimistic.
Using this setup I stuck a 2.75" group up at 300ish yards from prone 2 days ago (discounting 1 called flier caused by a flinch) with my A-bolt in .243 using this setup and some hand loads.