Burrard gives a good bit of coverage to these chamberless guns in his 3-volume work "The Modern Shotgun". While these guns used heavier than normal shot charges they alo had lower than normal velocities which kept the pressures in line. He gives some load data on them, but of course with Black Powder & Obsolete Smokeless ones, but they can serve as a reference as to what the loads should be. The gun may be somewhat light for handling 2Ľoz at normal velocity, which might produce a fearsome recoil.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra