Blueprinting and indexing

Blue printing, like with car engines means tightening up tolerances and clearances to make the mechanical parts work smoothly and last longer. Indexing is simply turning the barrel 360deg, stopping ever 45deg and shooting to see where the vertical axis is for the shot. Also as Salticon has said sometimes you can index to shoot in winds as well using your test information.

Why not BB air guns it work with bass boat props. Just give them the number they need and they can make a Bass boat come alive. It should work the same way with air guns, just need to know what they need to know.