Hank15 -- Does it make a difference what type/size shots you use? Or is the chart only referring to the "standard" 2 3/4" birdshots with 7 1/2 pellets?
Yes, no, maybe, kinda/sorta and I guess sometimes...
Effective and Ideal was both expressed in x to y range to cover the difference between LEAD small buck and small bird...Heavy buck, #4 and over will spread out a wee bit more but remember that there are far less pellets to cover the same area of space in the circle...
A choke’s designation is classified by how many pellets (as a percentage of the total in the cartridge) will fall in a 30" (76cm) circle at 40 yards (36m).
Steel shot is usually a bit wider spread, about one choke up to achieve the same pattern...Bismuth and Heli pattern about the same maybe a even little tighter...
Shot spreaders or diffusion chokes work opposite of normal chokes--they are designed to spread the shot more than a cylinder bore, generating wider patterns for
very short range use.
A number of recent spreader chokes, such as the Briley "Diffusion" line, actually use rifling in the choke to spin the shot slightly, creating a wider spread...one thing to note that when buck is fired from a rifled barrel it makes a doughnut shape on the patterning board...
Consider 5 or 7 yds, the normal training distances, depending on choke it would be like tossing from an apple to a cantaloupe sized load down the hallway, that's what your hitting with, no massive, side of wall to side of wall coverage, an apple to a cantaloupe...
Where chocking plays a big difference is with birds (clay or real) because to tight of a choke can easily miss them where with too wide a choke they fly through the pattern...If I flush a bird with a full choked gun I'll wait until they're 25, 30 yards away before shooting because if they're too close you can really damage a lot of meat as well as missing as the tight spread hasn't opened up enough...If I'm using an Improved Cylinder choke then I'll take them as soon as I can mount my gun because they'll very soon be out of range, the spread will be far too wide and only a lucky hit to the head would kill them...