RE: Detuning
Straightarrow, when you switch from field points to broadheads, you've changed the total length of the arrow, which moves the arrow's balance point. You've added to the arrow's frontal surface area. You've added wings to the front of the arrow which contend with the arrow's fletching for control of the arrow. Too many changes to assume one can tune a bow to perfectly shoot both at the same time.
For most people it won't matter. Either they don't shoot at distances wheretuning problems will eventually manifest themselves, or they don't shoot tight enough groups (at the short distances most people do most of their shooting)to really notice a half inch improvement in group sizes. Just because they can tune their bows to shoot both broadheads and field points to pretty much the same point of aim, within their skill level and average shootingdistance, doesn't mean the bow is actually perfectly tuned for both.That's simplyall mostpeople are looking for.
On the other hand,nobody can tune a bow better than their actual shooting skill allows (except in cases of blind luck).I suppose one could then make the argument that perfection is relative. What is 'perfectly tuned' for a backyard duffer would not be anywhere closefor a world class competitive shooter.
When I want to shoot broadheads, I forget about field points altogether. I tune the bow to shoot the smallest, most consistentgroups possible with broadheads. My field points probably won't strike the exact same point of aim, but why would I care? I'm looking for the best accuracy and consistency possible with broadheads.
Tuning to shoot broadheads and field points to the same point of aim is a compromise tune, done for the sake of convenience. It's not an indicator of a perfect tune.