Finris,
At the range, I shoot the Wolf off a concrete bench with a short Harris bipod. I shot those groups with a silly (I think Caldwell, from Midway) rear bag that I felt was too short and way too malleable. I think I had to squeeze the bag for around 20 minutes of elevation - that kind of thing just doesn't help your technique.
Last week I replaced that rear bag with a much stiffer short-ear Protektor bag...
In the field, I use traditional prone technique (adapted, of course for the bipod) - no rear support. However, I will be testing AR Tactical's lightweight poly-bead-filled rear support bag this weekend on prarie dogs. We'll see...
