[Buffalo Head]

There is not a separate primer, per se, in rimfire ammunition. Primer mix is forced into the internal cavity formed within the rim of the shellcase. The firing pin in rimfire firearms crushes the rim, which ignites the primer mix contained in that peripheral cavity which in turn ignites the propellant powder.

[jwparkerjr]

Ah, that makes sense! A million thanks. I’ve wondered about that for years but never came across an occasion to ask about it!