Every test I have ever done ( I have done many) always showed the heavier arrow penetrating better, but there is a sweet spot for most bows. And this was irregardless of arrow type or diameter.

I agree with almost everything Arthur and TFOX have stated except the thing about the thin walled aluminums. I get better penetration with 2213's than I have out of any carbon arrows I have used and certainly not any less than some of the thicker walled aluminums I have used. It won't matter how thin the wall of the arrow is, if it has the same spine it has the same resistance to bending. The diameter of the shaft makes up the difference for the thicker wall. So the only factor in penetration would be the larger diameter of the arrow. However in a well lubricated target like a live animal I don't think it would matter too much.

The thin walled arrows do dent easier though when you hit them with a different arrow.

I'm not saying one of us is right and the other is wrong, I just haven't seen this and I would need some pretty decent scientific evidence to the contrary to change my mind.

I have LOTS more to say about this thread, but I think I will bite my tongue for now. Those that know me know what I am thinking I'm sure.

Paul