There are about five different 400-360 cartridges which differ from each other by slight variations in the bullet diameter, weight, and powder charge. They all used the same case with slight variations in neck diameter to accomodate the variations in bullet diameter.

The 400-360 2-3/4 Rigby Flanged had 41 grains of Cordite, and a 0.360 inch bullet of 314 grains weight.

The rimless version was manufactured by the simple expedient of putting the flanged case in a lathe and machining off the rim and cutting an extractor groove. It carried the exact same load as the flanged version. This was the only rimless cartridge among the various 400-360's.

It was for a Rigby magazine rifle that must have been custom ordered with no more than a handfull made. But the cartridge was listed in one of Rigby's catalogs. It's obvious that turning cases in a lathe is not a mass production technique. Examples of this cartridge are quite rare these days.