The term belted magnum or belted case refers to any cartridge, but generally a rifle cartridge, with a shell casing that has a pronounced "belt" around its base that continues 2–4 mm past the extractor groove. This design originated with the British gunmaker Holland & Holland for the purpose of headspacing certain more powerful cartridges. Non-shouldered (non-"bottlenecked") magnum rifle cartridges especially could be pushed too far into the chamber and thus cause

catastrophic failure A catastrophic failure is a sudden and total failure from which recovery is impossible. Catastrophic failures often lead to cascading systems failure. The term is most commonly used for structural failures, but has often been extended to many oth ...

of the gun when fired with excessive headspace. The addition of the belt to the casing prevented over-insertion. An example of an American adaption of this practice is seen in cartridges like the

.458 Winchester Magnum The .458 Winchester Magnum is a belted, straight-taper cased, big five game rifle cartridge. It was introduced commercially in 1956 by Winchester and first chambered in the Winchester Model 70 African rifle. It was designed to compete against t ...

, also a shoulderless heavy magnum. Many subsequent cartridges of "magnum" nomenclature were based on the original .375 H&H cartridge, so over time the belt became something of a standardized attribute, expected as part of a "magnum" cartridge. Many cartridge designs of the last century include this belt, but do not really require it. Since the beginning of the 21st century, there has been an ever growing trend toward beltless magnum cartridges, virtually all of which are heavily shouldered designs that obviate the original motivation for a belt.

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