I finally realize after shooting in basement why a 233gr Snuffer will hit target at a different spot than a 233gr Zwickey Delta. The broadheads have different balance points, changing FOC on the same shaft from 24.3% to 23.6%. Resulting in the change in right/left impact. Probably obvious to many of you. I used to assume it was flight characteristics of different broadheads. Maybe why a broadhead and field point of the same weight strike different right/left. The extreme example of a long 200gr Grizzly vs a short fat 200gr field point, would change %FOC even more.

I shoot the real long 3 blade vpa.  I have to tune my arrows a bit stiff with a field point to be perfect with the head

Kind of blows the theory that traditional archery is simple.   

I would think a change in dynamic spine is occurring with the foc change causing the variation of impact.
How much of a difference left/right are you seeing?

Katman,two inches at 17 yards.

Might be 2 vs 3 blades. ...
Seems odd that such a small difference would cause such an impact change.  But it could be all in the tune.

Don't know much about FOC cause I don't worry about it. But I thought it was measured from BOP to valley of the nock.
Hap