"Smith calls it the “TEMPO” operating system, but it is really a classic gas-operated, locked-breech operation, except the barrel itself is the op rod and piston. When you have the barrel out of the sleeve, you notice there are six radial fins on the barrel that act as piston rings, three skinny ones out by the muzzle and three fatter ones toward the breech. There’s also a gas port out toward the muzzle end of the barrel. When the bullet passes this port, gas passes back into the space between the barrel and the sleeve, driving the barrel rearward until it meets a lug in the frame which causes it to rotate through 90 degrees, unlocking it from the slide."The whole review is online at the link, no punches pulled.
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