That's it! The Steyr people measured barrel length in centimeters, not inches. So for American catalogs the original measurements 45 cm = 17.716", 50 cm = 19.685" and 60 cm = 23.622" were listed as convenient 18, 20 and 24 inches. Post-WW2, a silly US law prescribed a minimum rifle barrel length of 18". So Steyr, in the interest of Stoeger, made the 6.5x54 barrels a wee bit longer to make them importable to the USA.