This is too funny New York Hunter. Read the post that I just added to this forum. I had the exact same problem as you with my 11-87 and those slugs. My 11-87 only shoots Lightfields good. That is it.
And even with those I think I should be getting a tighter grouping at 100 yards.
By the way, I blogged my experience shooting the same slugs you mentioned above. You can read it if you like.
http://www.empirehunting.com/new_york_hunting_blog/new_york_deer_hunting_Sight_in_early.aspx