RST carries a full line of 2 1/2" 16ga shells at nearly the same price as you will pay for 2 3/4" shells and Graf & Sons carry 2 1/2" primed hulls and components. Why take a chance on ruining a fine weapon like a drilling.
My personal 16ga drilling has factory 2 3/4" chambers but I have an older one coming with 2 1/2" chambers if all is well with it I'll have the forcing cone lengthened and the full chokes opened but will leave it at 2 1/2" and just load shells for it. I'm already loading 2 1/2" for my 12ga bird gun so it's not a big deal.
