The most important question here is.. are you getting consistant patterns with the broadheads even though they dont shoot exactly the same as the field points?
If you sight in your bow for the broadheads and your getting consistant patterns(where your aiming).. thats all that matters.
Most fixed blade broadheads do shoot different than field points. If there is any inconsistency in the pattern on the same arrow type(weight, length, and fletching), its usually due to a broadhead being slightly off center on one arrow… for example, if your shooting 3 arrow groups and one arrow is always 6″ off… that broadhead probably isnt centered.
You need to take into consideration that the fixed blades act as wind rudders so arrow flight is being stabilized at the front(broadhead), and at the rear(fletching) of the arrow. Just the arrow flex when being release from your bow can throw your shots off slightly when you add the extra *rudders* on the front of the arrow. A field point is going to react like a dart and correct itself in a different manor than the broadhead. The fixed blade broadhead will actually correct its flight faster than a field point.
blah blah blah….
Just sight in your bow to the broadheads. If you are getting a consistant pattern, you will have confidence when taking aim at your deer.