I do not think their brass would be a Magtec case. All I have seen that they use is drawn solid head brass.

The commercial brass companies stopped using balloon head and semi balloon head rifle cases and went to solid head cases in the late 1890's with the advent of smokeless powder. These companies did still use semi balloon head pistol cases up into 1930's. It has been suggested this may coincides with the end of cartridges loaded with black powder.

The CBC Magtec brass is shotgun brass of semi balloon head. I have several hundred of these cases formed to 577/450 accumulated over the years and they have served me well. They are however restricted to black powder only.