tnshootist,
I think a guy has to definitely use field rests to get the most accurate reading on how a particular gun will shoot in the field. As an example, I worked up a load for my neighbors Browning BLR and it would not tolerate shooting off any kind of sandbag type front rest. Held off hand it would give decent groups. Ironically, my neighbor has only one arm and can shoot that rifle better than anyone he hands it too. A somewhat bizarre match made in heaven.