Same thing happened to me this year Fred. I am shooting 465gr out of a 72# set up and i only got about 2" of penetration and a broken arrow in the front shoulder. I was shooting G5 Montecs so I don't think a mechanical would have done any better.

I think it really depends on where you hit in the shoulder. If you Tbone the "thick" part, not many arrows are going through. If you hit a little back in the scapula, it should punch through. Although, I will never again try to tuck one in there tight like I did with this buck. I'm going a little further back for some buffer on the big bodied deer here on out.