You can if you're only shooting one shot groups, which is pretty much what you're doing in the field.You can't shoot 1/2 minute angle groups from a 3 minute rifle.
Group sizes tell you just one thing and one thing only - how the rifle performs when its barrel gradually heats up. Since most field shots are taken with a cold bore, the importance of group sizes is greatly exaggerated unless that group size is measured with a cold bore for each shot.