Does not swing freely. Look at the detent when the blade is open, you will see that it has worn in and created a flat spot on the ball.
The ball detent (like the bearings) will far outlast the blade and lock on the knife, so again it's a moot point.![]()
Surprisingly, that flat spot on the detent ball has nothing to do with the function of the detent ball. The "sides" of the ball do, and they don't wear.