What limits rimfire ammunition to low-pressure loads?

The limitation of rimfire ammunition to low-pressure loads is primarily due to the location of the primer in the rim. In rimfire cartridges, the primer is situated in the rim of the casing rather than in a separate primer pocket, as seen in centerfire ammunition. This design inherently restricts the amount of pressure that can be safely generated within the cartridge.

Because the rim is the detonating component for rimfire cartridges, it is generally constructed from softer materials that cannot withstand high pressures. As a result, rimfire ammunition is designed to operate at lower pressure levels compared to centerfire ammunition, which can utilize higher pressures thanks to their more robust primer and casing designs. This means that rimfire cartridges are ideal for applications like target shooting and small game hunting, where low recoil and noise are helpful.