On some arrows I chronoed and tested,a 714 gr arrow had a momentum figure of .49.A 530 gr arrow from the same bow had a momentum figure of .41.That is 20% less.Penetration testing in man-made materials showed the same difference in penetration.It's noticeable.

I would expect a well tuned 550 gr arrow to blow through a whitetail most of the time but who knows what else was at work?

QuoteOriginally posted by Shawn Leonard:
150-200 never hurts penetration unless your BH is not sharp or the wind was blowing or ya plucked the string, as said way to many factors as to why the different results. I for one like a lighter 9gpp for trajectory and it is all that is ever needed for whitetail. Jason Westbrook has always said it best, a 500 grain arrow out of a 60# bow will penetrate better than a 500 grain arrow out of a 50# bow, one is a tad over 8gpp. and the other 10gpp. so what is the fuss about grains per pound. My 470 grain arrow can be the so called magical 10gpp. out of a 47# bow, what is so magical about that? It shoots flatter and hits harder out of my 52# bow! Shawn

Shawn, I agree. I have for the most part always used arrows in the 9-9.5gpp and a few times even lighter. I find my bow still shoots really smooth and quiet and I really like my trajectory. I have used arrows that were heavier and would again, but I just like the lighter arrows. I do some 3-D shoots and I like to practice with the arrow I will use for hunting. I can say I don't see much difference in a 510gr arrow vs a 600gr arrow out of my 57# longbow at 20-25 yards. I do however see a difference at 30-35 yards and from 40-50 yards it is much different. I mostly use 535-550 gr range and have had no problem at all with deer or hogs.  

I sure don't think you need to change anything, shoot what ever puts it in the right SPOT everytime, and flies perfect,and there will be no worries.

Although lighter than I really want, the last 3 Adult Midwest deer I have shot  have fallen to a 400 grain carbon with 100gr. Stingers at 196 ish fps.

They pass thru easily on deer, and stick in the ground firmly.

Apparently you prefer the 550 over 700, yet maintain some reservations. Ultimately you yourself need to have optimum confidence.

It is very likely and with little trouble that going with a ~30% Ultra-EFOC set-up close to 550 grains could vastly raise your confidence level with some self experimentation.

Over thinking this thing!
Shoot what you have most confidence in and stick to it.
If you keep switching and tinkering w/ your set-up you don't become as one w/ it as easily as if you stick and stay to what you have confidence in.
Been there done that!