Almost certainly going to have to reload for that cartridge... Winchester stopped producing rifles in the caliber in 1971, and not that many were actually produced to start with due to competition from the .22-250 drowning it out. I'm not even sure if Winchester's still making the round, they were doing rare, small runs of it a few years ago from time to time, but hardly any makes it to Canada. Brass is however available, and if you reload, you have a good cartridge there, but it's not at all practical trying to use factory ammo for it.