I also understood was Jack was stating.

"Measured constriction of choke will only give an approximate idea of what pattern to expect. This can be greatly influenced by various cartridges and the construction of cartridges with regard to powder, wad, shot etc."

I am glad that you put that in, as too many people judge what is stamped on the barrels or what they read on a gage. I have seen it more than once on this site, where someone bought a gun on an Internet auction and without having the gun in hand want to send the gun to someone to have the chokes opened because of readings given or what is stamped on the barrels.

Your last sentence sums it up.

David