Comparing a .17 HMR to a BB is like comparing a bicycle to a Corvette. There is no comparision. I see what you did though. You saw that a .17 HMR is on .17 where a BB is .177.. BUT a .17 HMR out weights, is longer, designed different, goes a hell of a lot faster/ further, is more accurate, and far more destructive then a BB.

As for a .17 HMR. I love it and can't wait to go hunting with it. I shot a few things down at the range, including peaches, pickles, coconuts to see the destructive power. I was impressed. It was also a pretty accurate rifle too. Probably won't go over 100 yrds with it though.