How should the LOP, DAH, and Chokes be determined.

[Bill Anderson]

If you lay your shotgun on it's rib to measure DAH make sure the sight bead is off of the table. A better way, that I have found, is to lay straight edge (common yard stick works in a pinch) down the rib out over the butt stock and measure the distance from the straight edge to the heel of the butt.
For the chokes, you need to measure the difference between the bore and the muzzle to get an accurate choke constriction.
LOP is generally measured from the front trigger to the center extreme edge of the butt plate or pad.

Bill

[Bill Murphy]

Strange that DAH is so interesting to some buyers of shotguns. This dimension is the most inconsequential of any stock dimension. Much as I feel that the Brits deal in more BS than anything useful, their "drop at face" is much more important than the stock dimensions we use.

[Theodore LeDurt]

I agree Bill, but the "drop at face" is seldom given. I thought that was because it can very from shooter to shooter. After years of worrying about dah, I have now found that dac is closest to my drop at face and more critical to shooting.