Already discussed to death: https://www.canadiangunnutz.com/for...unces-new-21-sharp-rimfire-cartridge.2476908/The Winchester 21 Sharp—a rimfire cartridge that utilizes a .22 LR case but a .21-caliber bullet.
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It does if you want to run a suppressor, assuming they make some subsonic ammo which I can only assume they will in the future.This cartridge does nothing a 22 WMR or 17 HMR can do better. Winchester should focus at producing ammo for the 17 Wsm and making a better rifle for it.