Depends on the weight of the arrow, but if you are spined "right" for 45#, recommendations probably would lead you towards a 100gr, or even an 85 or 75gr. Try this site, and it will guide you a little: http://home.att.net/~sajackson/eastonchart.html . Also TFOX probably has better info, if he posts up, he may have better specific info. But heavier BH on lighter weaker spined arrows can tend to create a little arrow "whip" and result in some inconsistencies.