Are you refering to a handling fitting? If so, one of my "short list" projects is a handling fitting try gun (one with adjustable weight, balance, and MOI's.
Yes, I was.
The MOI through the CG, butt, or any other point along the gun's long length is constant. That is to say MOI is the same for side-to-side swing and up-and-down swing.
Well, that simplifies matters. Multiple MOIs would be inconvenient, would they not? So the next step, on my part, is to construct a torsional pendulum and start measuring.
Actually, I am very interested in applying this technology to rifles, to see if I can determine why some specimens seem well balanced and lively, and others feel....leaden and dead. And I really appreciate your input and insight.