No shotgun will ever deliver an "even" pattern. "Even" meaning pegboard layout patterns. All patterns are Rayleigh distributions (OK to think of them as Normal distributions).
"Even" may have been a bad choice of words . . . although Mr. Brister used it in his book, with additional clarification:
"In the thousands of patterns tested by Oberfell and Thompson for their "Mysteries of Shotgun Patterns", the point is made repeatedly that the pure-cylinder choke (no choke at all) throws the most even patterns of all. That is, in layman language, the patterns have fewer patches or holes relative to the spread of the load." He goes on to mention Russian Olympic skeet shooter Eugene Petrov, who was the first person to shoot 200 straight at international skeet, with a gun that essentially had a blunderbuss-like muzzle.
