The .33 Winchester Center Fire / 8.6x54mmR (colloquially .33 Winchester, .33 WCF,^[2] or .33 Win) is a centerfire rifle cartridge designed and produced from 1902 to 1940 by Winchester Repeating Arms Company for their Model 1886 lever-action rifle.

With the new Model 1886 lever-action rifle, and appearance of new smokeless powders on the market, in 1891, Winchester Repeating Arms Company started to experiment with necking down the .45-70 cartridge. The first attempt, a .31-62 with a 200-grain bullet, reportedly resulted in pressures too high for the action. Only a decade later, the desired result was achieved with a new caliber when the .33 Winchester was introduced in 1902.^[1][3] Never popular due to lack of range despite high muzzle velocity (the 1886's tube magazine ensured that aerodynamic pointed-tip bullets couldn't be used except while single loading), the only other firearms offered in this chambering were the Winchester Model 1885 and Marlin Model 1895.^[1][4] The round was eventually replaced by the .348 Winchester in 1936, and ultimately discontinued by Winchester in 1940,^[4] although it is still currently produced in small numbers by other ammunition manufacturers.^[1]

A good round for deer, elk, or black bear in wooded terrain at medium range, it outperforms the ballistically similar .35 Remington and can be improved with modern powders.^[4]

• 8mm caliber
• List of cartridges by caliber
• List of rifle cartridges
• List of rimmed cartridges
• List of Winchester Center Fire cartridges

• Barnes, Frank C., ed. by John T. Amber. ".33 Winchester", in Cartridges of the World, pp. 83, 122, & 123. Northfield, IL: DBI Books, 1972. ISBN 0-695-80326-3.