I qam not surprised at Roundball's experience. I would not expect a Jug choke would have much, if any effect, on those stiff, hard, plastic shot cups needed to shoot steel shot. You need a fixed choke barrel, or a barrel with screw in choke tubes at the muzzle to affect steel shot in those cups. I found, in my modern gun, that a modified choke tube gave me full choke patterns using Steel shot in BB, and #1 steel shot sizes. Improved Modified gave full choke patterns with smaller size steel shot loads.
The real difficulty using these cups and steel shot in any MLER is getting those cups into the barrel Thru the choke! The bottom of the cups don't want you to get those cups down past the choke. They shoot OUT fine, but going in is a fight.
For those reasons, I don't recommend using Steel shot in a MLER, unless you are going to accept the range limitations of a cylinder bore shotgun. You will see a bit of tightening of the pattern firing steel shot out of an cylinder bore barrel, because the steel does not distort in the barrel, and the stiff cup delays the separation of the shot from the cup once it leaves the muzzle longer than a standard shotcup does. But, we are talking about Improved Cylinder vs. Cylinder Bore patterns, for the most part. Some loads may tighten up to Skeet 2 or Skeet 1 patterns. Every little bit helps of course, as you can extend the killing range of a given shot size pellet and pattern by 2-5 yards for every increment in pattern performance. Mostly, with a cylinder bore shotgun, you want to use more shot than what modern gun shooters can load in their casings. The extra shot helps to fill the pattern with more pellets, and that gives you more range and killing power at the longer ranges. I still consider any MLing shotgun to be a 40 yard gun MAX, altho birds have been killed at further distances than this with such guns and steel shot. I just don't expect the average bird hunter to be capable of placing his pattern on game birds at ranges over 40 yds. with any confidence.