Raimey,
Yes, the 45-70 rim is thicker than some similar Brit. and European cartridges, but some Brit. cartridges came in two different rim thicknesses in the same nominal designations. The MB rim is over 2mm and being able to ID this rim is a great help in IDing the cartridge, but misIDing it sends everyone down the wrong path. The 45-70 rim can be modified to fit either "thin" or "thick" rims as well as MB cartridges. The head diameter needs to be within range of the target cartridge. The 50 cal Win. and Sharps cases can be adapted to other Brit. and European cartridges in a similar manner.
Mike