According to the 1914 Franz Sodia, Ferlach, and the 1929 Steyr factory catalogs, the standard M1910 barrels were 50 cm = 19.7” for the full-stocked carbines and 60 cm = 23.6” for half stocked rifles. The Sodia catalog mentions non-standard barrel lengths up to 75 cm = 29.5” barrels as available on special order. All the time you could order half-stocked carbines with 50 cm barrels too, if you did not like the extra wood to the muzzle of the full stock.