A small, simple question, one I feel like I should know the answer to, but I really don't: you are bucking a log (into firewood or long lengths, doesn't matter), you cut say 3/4 or 4/5 of the way thru and then roll the log to finish the cut. When you stick the bar into the kerf to finish the cut, why does it cut so much better and easier and sometimes a bit faster when you do it with a pushing chain (top of the bar) than with a pulling chain (bottom of the bar)? In either case, the bar is inserted equal depths into the kerf.