I have started sending back carbons to the MFG when I see an arrow off spec, or inconsistent spine. What is more important to me is inconsistent spine I see with arrows these days. Out of 12 arrows, I might get 4-5 that are worthy of fixed broadheads and hunting. Some that have inconsistent spine are not even worthy of target practice.

I made a spine tester out of a dial indicator and wood. I did this for traditional cedar arrows, but works equally well with carbons. It has a 2lb wieght and I generally measure at 26" (traditional convention), but one can easily change it to AMO by moving to 28" and different wieght. But my main purpose is to measure spine variations.