Try the 2 3/4" Federal FC in a #6 if not that get a Win 2 3/4 1 1/8 #6 .
The old Federal magnum shell in a 2 3/4 shell was a killer in a full choke and should be a tight pattern in the flight control shell. The pre flite control are available from Rogers Sporting Goods
Let us know how she goes.
My first post I was on 12 ga and not 20 gauge loads.