I for one would not mix British & German data unless you know you are comparing apples to apples. Per Wirnsberger, the chamber of a German double under the 1912 rules pushing OVER 55.5 grains, 1 1/4 oz, of shot for a 12 bore with 70mm chambers or OVER a 1 oz payload in a 16 bore should not be chambered unless the scattergun has experienced special proof which is in excess of 75% over the service load.

Cheers,

Raimey
rse