Many cartridges use a combination of calibre and charge weight to define them. For example; .40-110 Winchester Express is .40" calibre with a 110grs. black powder charge. This convention holds good for many others such as the 40-50 Sharps; 38-90 Winchester express; 32-44 S & W target; 45-70 Government etc.
However, Logan shows a reversed format for rimfire cartridges such as the 56-46 Spencer (.46 cal.); 56-50 Spencer (.50 cal.); 56-52 Spencer (.52 cal.). Can anyone please explain this reversal of calibre and charge?