I know the guy who fired 3" Brenneke slugs through half and full choke in IZH-27 "Baikal" chambered 2 3/4" - nothing happened, but the kick was pretty good, as the guy mentioned. But it was Baikal and fixed chokes.
In your case Briley thin wall tubes are the most delicate question. Usualy Briley titanium tubes fly away with buck shot all together


Geno.