I also strive to optimize my hunting setup and give penetration one of the key regards; not because it is always necessary for textbook perfect broadside hits, but because if/when an arrow strikes an area that is difficult to penetrate, I want my arrow to travel as far as possible to reach vital organs (ie; through a shoulder blade, ham, brisket, etc).

I've found that an arrow of 9-13 grains per pound of draw weight seems to optimize my setup. Lighter arrows offer the advantage of a flatter trajectory and greater leeway in range estimation, but that's it. Arrows of weights that I prefer offer better penetration, make a bow very quiet, make the bow sweeter to shoot due to less hand shock, may extend the life of the bow, and still provide a reasonable trajectory. Going heavier, the arrow's trajectory becomes too highly arched to manage well over even close distances; accuracy suffers and diminishing returns is reached. My own hunting arrow sets range in weight from 600 to 775 grains for the 60 to 70# bows I hunt with.

Arrow weight alone is but one part of the equipment equation in considering the optimum hunting arrow. For example, broadhead design plays another key role, particularly in regards to penetration and tissue damage. (I prefer a long, slender, cut-on-contact, one-piece, 3 blade head...but that's another thread.) Every bowhunter must make equipment decisions based on their priorities and needs, having to balance the often opposing effects of each variable he chooses. The archer insisting on a light, fast arrow may do well for tough-hit penetration if he couples his light arrow choice with a slender, cut-on contact 2 blade head. Of course, arrow weight becomes more critical when slower bows, particularly stickbows or early compounds, are the weapon of choice.