A good fit isn't just about measurments and clearances, it's also about proper mounting and conformation.
IMO, Chuck came closest to nailing it. LOP, given in inches, is practically useless for
predicting gun fit.
I have 11 shotguns that all fit me perfectly, as I define it. Which is to say, with the exception of my one trap gun, I can mount all of them from the low gun position, to shoot any target (game or clay) presentation with the gun virtually never dragging on my body or clipping my armpit on the one extreme, or hitting my nose with my hand on the other extreme. Each of the 10 guns will shoot exactly to POA with a 50/50 pattern from a dynamic mount. The LOP's vary from 14.25 - 15".
As a way to communicate, we define LOP as the distance from the center of the trigger to the center of the butt. But,as I said, this measurement in inches has little to do with predicting fit, unless you happen to be talking about one gun or guns with identical grip shapes.
Try this....make a fist and place it on the table in front of you. Extend the index finger until the pad just clears the middle finger. Imagine the distance from your index pad to your armpit. Now extend your index finger in stages from this position to full extension and see how that dimension changes. The same thing is at play when you grip a target gun with a tightly radiused pistolgrip and then a game gun with a straightgrip. They can have identical "LOP", yet one can be effectively too short and the other too long. The same is easily seen with guns (Beretta/Browning O/U's, for instance) that have 3-position triggers....moving the trigger definitely changes the measured LOP, but does absolutely nothing to alter gun fit.
The best LOP is not a number; it's the one,
through trial and error with a particular gun, that is short enough to virtually eliminate mismounts and long enough to aid consistent eye placement and ,therefore, consistent shot placement. Find that length and you'll also have coincidentally prevented a sore nose.
