The 6mm Remington rifle cartridge, originally introduced in 1955 by Remington Arms Company as the .244 Remington, is based on a necked down .257 Roberts cartridge using a .24/6mm bullet. Known for a combination of high velocity, long range, flat trajectory, and accuracy, it is suitable as a dual use hunting cartridge for both medium-sized big game and varmints. When used in the less common earlier slow twist barrels, it offers exceptional range for varmint applications. While not as commercially popular today as the .243 Winchester, the 6mm Remington enjoys a slight ballistic advantage and continues to be popular with handloaders and custom rifle builders.

The .257 Roberts, also known as .257 Bob, is a medium-powered .25 caliber rifle cartridge. It has been described as the best compromise between the low recoil and flat trajectory of smaller calibers such as the 5 mm and 6 mm, and has more energy, but is harder recoiling, similar to larger hunting calibers, such as the 7 mm and 7.62 mm.