RE: Shotgun Barrel Length...
I agree with all the replys on this post. The new powders, shotshell components are greatly improved. In an article I read years ago stated that the powder is burned up in about 25" of barrel.
I've hunted ducks, geese and turkey for years with a 26" barreled 12 ga Rem 11-87SP with no complaints.
The most important thing to do is to pattern the shotgun with various loads and choke combinations.
Case in point: I got a Remington choke recently that was stated as full choke (steel, lead, and tungsten). I took my 870 Super Mag out and tried this choke with 3 1/2" BBB steel, #1 Steel, 3" #4 steel, 3" #4 lead and 3" BB Heavy shot. I then replaced the choke with my Rem-choke modified tube and shot the same shells. All the loads shot tighter, except the #4 lead, with the modified choke. I then shot the #4 lead with my Rem-choke extra full and found that this shot tighter than my new choke.
Looks like I wasted $36 on that new choke. I would like to try a Kicks choke. I hear they are very good. Just wish I knew someone who had one cause they ain't cheap.