If you are interested in the .177 vs .22 debate there was an article written in the Air Gunner magazine a while back (could be 2 or more years) comparing the 2 calibers in terms of ballistics and penetration, incase you cant find it on the net , it was proved that the difference in energy retention between the 2 was so small even in terms of sub FAC air rifles it was not worth the fuss, If I remember correctly it was about 0.9ftlbs out to 30 yards (might not be correct, but I do remember it was not a lot), the penetration test concluded the .177 penetrated considerably more due to the smaller