I have a IC/M o/u. That I hunt with almost every year. It is a sweet gun for pretty much everything, and this sorta explain why. It makes me a much better wing shooter than I actually am.

I found this to be the most interesting finding in the pattern study: 


"The real surprise, to me at least and, I believe, to most other shotgunners, is the performance of Modified. The pattern spreads steadily from the muzzle until, at 25 yards, it is a good 25-inch killing pattern. It then maintains this outer killing pattern for a full 20 yards, neither spreading further nor deteriorating, and giving excellent performance from 25 yards to 45 yards, and a still-creditable 20 inches way out there at 50 yards.

Modified may well be the single most useful all-around choke of them all."       



http://www.shootingtimes.com/long-guns/longgun_reviews_st_headintheclouds_201002/#ixzz4BRZ5rp1p

I know there had to be a scientific explanation for all of the anecdotal evidence, my own included, as to why a modified choke is so popular.  It just gets the job done for most uses.

However, I must say that on rising birds (quail, etc.) or when doves are really coming in close, coming down to feed, I do much better inside 25 yards with improved cylinder or even skeet.

When shooing an 0/U or SBS I do like that second barrel to be modified, even if the first one is skeet. If I miss that first shot, the bird (or clay) will be far enough away to need the density of modified.  That's just coming from an old shotgunner who is nowhere close to being a crack wingshot.  I need all the help I can get.

Something that video shows not discussed in the article is the effect of shot stringing.  Not all shot arrives at the target at the same time.  And if the target is moving, that means that part of the string may arrive ahead of the target, some on the target and some behind it, irrespective of how the pattern looks on a pattern board.

That is why larger bore shotguns tend to do better on moving targets, all other factors being equal.  A 1 ounce load of #8 from a 12 gauge will have a shorter shot string than the same 1 ounce from a 20 gauge at the same distance.  More pellets in the 12 gauge are likely to actually hit where you are expecting.  It may not seem like much of a difference in the diameter and depth of the shot cups, but it makes a significant difference down range, or certainly seems that way to me.

I do much of my upland hunting with a nice, light, quick handling 20 O/U.  I recognize that I am giving up some effectiveness on flying targets compared to any 12 gauge I might bring, but accept that for the lighter field carry and more nimble handling.

Next dove season I'll have to bring out my old Savage 220A 28 gauge and see how I do. 

I usually use a 16 gauge Winchester model 12 and do best with that, but I'll admit that I haven't given the 28 the workout it deserves.