55, I used to play with different bow/arrow combos to try and tweak more ke out of them. The answers that were already posted are right on the money. A bow only has what it has. In my rather crude testing, I did find a pattern. Without changing anything on the bow, a heavier/slower arrow always developed more ke in my tests. But I am talking about #`s like 68ke vs. maybe 69.5-70ke. Not enough to sway your preference on arrow weight. I saw your earlier post about your new champion, 75ke with 27" draw. I did not want to burst your bubble, so I did not respond. If there are any bows out there that could develop over 65ke, at 27" draw, I don`t know about them. Heck, I only develop 66.75ke with a 29" draw. I have had bows that would get me into the low 70ke range at that draw length, but I don`t care if my arrow buries 2" into the dirt, or 6" into the dirt, after passing through the deer I shoot. 57-60 ke will do anything you need done, though I would follow Matt/PA`s advice, on really big game go with a heavier arrow/broadhead combo.