Jeff, when you have a field point, your feathers are doing most of the guiding and correcting. When you put a BH on, now you have introduced another planing varible.
There is no limit to accuracy.
I tend to give the archer the benefit of the doubt. If he's bare shafted his FP's.....and he's tuned....then there shouldn't be a discrepancy.
I don't think I'd be making nock point adjustments without bare shafting, FIRST.
Aren't we supposed to eliminate "issues"....one at a time? Why do so many compound shooters feel like they don't need to bare shaft?