But explain why I can shoot one carbon with a practice tip, one alluminum with a practice tip, and they will hit the area im shooting at, I shoot one aluminum with a broadhead and one carbon with a broadhead, the aluminum will hit exactly where I want and the carbon will hit 3-4 inches lower...but yes they are different diameters. My carbons are Easton Excell St 400's and the aluminums are Easton 2314's.
ORIGINAL: Arcus Venator
Your carbons are probably a different diameter than your aluminum arrows. That would cause the realtionship between the arrow and the string to change.