I am of the impression, based on my own experience, that largely 1 oz (typically faster loads) like a full choke. There have been exceptions such as I found my 870/1100 guns seemed to break better with a mod choke over a full. But with my XT and BT100, there is a very noticeable difference when I went full with the same 1oz loads. I've tried several and for me, with my gun and my 1oz loads, they prefer a tighter choke. It should also be said they are 1290 1oz, so I believe the speed has something to do with it too. I used the same full choke from the 16 as I do from the 27 and the same 1oz loads. A few weeks ago while shooting some rounds from the 27 I decided to use the bottom barrel of my XT which has an IC installed (first shot of doubles) just for kicks. I was surprised that I still hit the targets, some pretty impressively much to my surprise.