The old RWS BB or CB Caps were virtually silent from a rifle. In High School I shot a few hundred of these from my Model 75T Winchester and all you could hear was the striker fall! Modern Remington & CCI CB Caps aren't quite so quiet from a rifle.

Nothing is quiet from a handgun because of the shorter barrel and Barrel-Cylinder gap in revolvers. Not as loud as a .22 Long Rifle, but far from quiet. This includes the RWS caps.

At reasonable ranges for extremely low-powered ammunition, less than 50', they are quite accurate from either a rifle or handgun in my experience.

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Gunsmithing since 1961