Belted Magnum cartridges were the original magnums, designed by Holland & Holland for the purpose of headspacing more powerful (at the time) cartridges. The belt feature allows for consistent headspace of cartridges that have little to no shoulder in the case geometry. The origin o these cartridges dates back to the early 20th century and the .375 H&H Magnum is the father to most modern belted magnum cartridges.
