I have thought and have heard that using a .177 in a barn shooting birds is better because of over penetration. But I wonder if I have it wrong. Example: when shooting high power silhouette a caliber smaller than 243 is not allowed because of target damage. Thinking about that made me wonder if a .177 may be the most likely to poke a hole in a building when shooting thru a bird or a bad shot hitting a steel panel. I have some extra panels and set one up behind a steel target at 60 yards. I was surprised to see the holes made.I thought I would just make a dent shooting a JSB heavy. What is your thought?