RST makes a 7/8 oz. 2 1/2" 16 ga spreader load of the appropriate pressure for a European double built in the 1920's. I've used them some for grouse & woodcock & I prefer them to the PolyWad spreader load.
Depending on your intended use if the gun truly is choked full & fuller you might want to consider opening the chokes as some point in time but I would pattern it & shoot it for a while before doing so.
IMHO super tight chokes are pretty useless for most types of shooting where a 16 ga is appropriate.
