...tighter choke constrictions have a following in buckshot country.
For example:
http://www.kicks-ind.com/mm5/merchan...ode=BuckKicker
The load used by the OP does
not use a flite control wad, but has the pellets stacked in a slightly offset spiral within a 3/4 length shot cup. As a result tighter patterns will require a greater degree of choke.