Ok my 2 cents for what it's worth! i think 600 grains is a bit over kill, say what you want but if you have more than 68 pounds of KE you can pretty much take down any animal in North America.. so why sacrafice speed if u dont have to?? Here in AZ
where the big bulls are plentiful, i know several guys who have smashed bulls with minimal KE.. and some that swear on mech-blades with close range shots due to the amount of KE they pump out.. For the record i will be hunting bulls this year in AZ, and my set up is currently 425 4000 vapors 100 magnus buzzcuts. some say it may be light but i amsmashing bullseyes out to 65yrds and my arrows fly as quiet as a blow dart.... and hit like a hammer....[8D]