This spare barrel has a single port on the top of the barrel, not multiple ports on either side like a magna-port. Was this standard for S&W?
The traditional trapezoidal cuts that MNP uses are patent protected so everything else has to look like something else. Is your port the single-cut , oblong shaped port just back from the muzzle end?
If so, I think S&W called it "Power Porting" and it wasn't used on any other models that immediately come to mind .... but I don't keep up with that stuff anymore.
These days, S&W is more about external compensators that in-barrel porting.
