I was thinking of switching to carbon arrows for hunting.  I shoot 51lb bow, 31" cedar stiks with 125 grain heads.  What size carbon shaft do I need?

I'd say 500's but don't buy them on my word...

Bakes

We need to know more about the bow , like longbow or recurve is it cut past center, actual make and model would help. What is your actual draw length and how many pounds is the bow at your draw. Probably get ya darn close with that info. Shawn

Shawn will steer you in the right direction he's real good at setting up carbon arrows he has helped me in the past.

Carbon Express 250's work for me with similar set up

I shoot an Allegheny Mountain bow made by Bill Kerner.  It's a recurve and pulls 51lbs @ 30". My draw is 30". It appears to be cut past center.