The.260 Remington cartridge was introduced by Remington in 1997. Many wildcat cartridges based on the.308 Winchester case had existed for years before Remington standardized this round.
The 6.5-08 cartridge was created simply by necking down the .308 Winchester Handloaders and wildcatters can easily form .260 cases by necking down the 7mm-08 Remington or necking up the .243 Winchester (both based on the same .308 case). Since the parent cartridges were readily available for low cost, the 6.5-08 was often an economical alternative to cartridges such as the 6.5×55mm. What the 6.5-08 provided over the .243 Winchester, .308 Winchester, and to a lesser degree the 7mm-08 Remington was bullets with excellent ballistic coefficients and sectional densities.
Since the 6.5-08 was a wildcat cartridge, variations existed between cartridge chambers depending on the reamer used to cut the chamber. Furthermore, depending on whether one chose to form the case from .243 Winchester or .308 Winchester influenced the neck thickness and therefore the dimensions of the cartridge. A cartridge formed for a specific rifle may or may not successfully chamber or worse may reach dangerous pressures in another. Standardizing the cartridge addressed the issues owners experienced when it was a wildcat.