7mm Remington Magnum
From Wikipedia - https://en.wikipedia.org/wiki/7mm_Remington_Magnum
The 7mm Remington Magnum rifle cartridge was introduced as a commercially available round in 1962, along with the new Remington Model 700 bolt-action rifle. It is a member of the belted magnum family that is directly derived from the venerable .375 H&H Magnum. The original purpose of the belted magnum concept taken from the .300 H&H Magnum and .375 H&H Magnum, was to provide precise headspace control, since the sloping shoulders, while easing cartridge extraction, were unsuitable for this purpose. Improved cartridge extraction reliability is desirable while hunting dangerous game, in particular when a fast follow up shot is required. The 7mm Remington Magnum is based on the commercial .264 Winchester Magnum, .338 Winchester Magnum, and .458 Winchester Magnum, which were based on the same belted .300 H&H Magnum and .375 H&H Magnum cases, trimmed to nearly the same length as the .270 Weatherby Magnum.
On its introduction, the 7mm Remington Magnum substantially usurped the market share held by the .264 Winchester Magnum, which went into sharp decline in popularity and sales after 1962. Remington has offered Managed Recoil ammunition for achieving reduced recoil when shooting and for generating less meat damage when hunting smaller game.