Many votes for the 222 Remington as an accurate cartridge. MD's point that specialty cartridges likely have custom barrels may be a major part of the "inherently accurate argument". Most choosing a less popular cartridge like the 222 Remington, 6BR, or even the 260 are likely getting a custom barrel and bedding job. You don't buy a Ruger American or Savage Axis in .222 Rem.
