So, applying a little logic and a lot of extrapolation, if one is dealing with a shotgun with unfamiliar markings or no markings at all, the dime test MIGHT indicate that it COULD be choked IM or F or at the other extreme C or IC. Or, it could indicate neither one depending on the bore diameter. What I don't get is, how could anyone who can add prefer a picture of a dime in the muzzle versus being told the actual dimensions to .001" of the bore and choke.
The problem with the crook of the arm/LOP test is the whole problem of measuring LOP from the trigger to the butt. Real, effective LOP is a function of where the hand falls - or is forced to be in the case of a full grip instead of a straight grip - relative to the butt. There's a lot of latitude in usable locations of the trigger finger which is why double triggers can be used. But a tightly curved grip forces the hand further forward than an open, or straight, grip. My recollection is Michael Mcintosh addressed this in an article once.
If one knows by experience what length works best for him, the crook of the arm test might be more valid than the distance from the trigger to the butt. If the stock feels long (or short) by comparison when held this way, then the LOP is long (or short), regardless of what the trigger to butt measurement might be.
Roger
