In my opinion, books give you an idea what the chokes should be. In the case of L.C. Smiths you ordered the gun with chokes you wanted. You told them I am going to be shooting said amount of drams, 7/8 oz shot, with a certain wad, etc. and they would make the chokes to your specifications. This was confirmed on the hang tag.
With today's store bought guns they mark mod/full, etc. Every different shell even with the same oz. shot will give you different patterns.
The only real way to tell is pattern your gun with the type of shell you will be using. Some books specify shooting 10 rounds of each type shell at the range you want and see what patterns the best. Also tells you to bench rest it for consistency.
