Howcome ?

[Zazu45]

HI guys.

I bought an "Undertaker" coke tube for my Remington 870 Express the other day.
At the same time I got two boxes of Winchester Supremes 3in. mag. shells (STEEL SHOT), one with no2 and the other with BB.
Next I went to shoot a few patterns. As a reference I shot few with Winchester Super double XX 3in mag. 1 7/8 oz with BB.
Weird thing was that the lead BB gave 85 % ,Steel no.2 gave 50 % and steel BB gave 60 % .
Everybody said that steel shot would pettern tighter than lead , what happened ???
My "undertaker" is .700 constriction (model 08675) and the packaging states:"For shot size BB,BBB,& T shot.
My only guess is that I got a "modified equivalent" instead of a full choke equivalent.
Or am I simply using shot that is too small for that constriction since pattern % seems to go up with shot size ?
By the way, how do "T" size shot perform on geese ?
Still it is a shame since I was looking for something to use with 2 and BB.
Anyway any feed back appreciated.

Thanks. Denis