You know what my favorite bags are? Homemade ones out of old bluejean pants legs and filled with sand. Sew up one end really tight. Fill about 3/4 full of sand, then sew up the other end. They work just fine. 2 in the front, 1 in the back. That's how I shoot all my groups, unless I decide to take the Caldwell tackdriver bag for the front, and use a sandbag for the rear.
Caldwell TackDriver Shooting Rest Bag Nylon Green Filled