Dennis,
That is usually how I measure drops as well. Upside down on a flat surface. It is important though to make sure the sight bead is off the edge of the surface, since it can effect the measurement by quite a bit.
I too have noted a couple of original Parker's that the actual dimention measurement was a bit off from order records. Maybe by 1/8" or so.
Actually, I think that depending on the gun, the method of using the ruler extension off the rib is more accurate since if the rib is concave, it will give a different measurement than resting on a table. But, unless the rib is a French swamped style or something, the difference in measurement will be very little.
And the actual point that you measure at makes a difference. As you say, the measurement at the tip of the heel could be different from the dimension at the spur.
__________________
B. Dudley
|