Hello, Drakejake. The Model 31 is essentially the same gun as its predecessor, the M28. The 31 has the pinned, external rotating extractor and the safety levers/slidestop lever are slightly different in shape, IF I remember correctly. My Model 28 with its factory fixed sights seemed to've been sighted in dead on at about 200 yards as it was way, way high from the factory at normal ranges, but I noted that the rear sight blade on the Model 31 was lower and the few I shot seemed to be pretty well "on."
Large and heavy for caliber, the Model 28 and therefore the Model 31 grouped pretty darned well and were reliable in my experience which is admittedly more with the Model 28.
The only downside I observed with the Model 31s and 31PKs that I saw were that the edges of the front sight seemed rounded a bit more than I liked, but since integral to the slide, I figured that occurred during the final polishing before bluing.
The major problem I see is if you do need replacement parts, they might be very difficult to find.
The picture below is of my Model 28 after some custom work: Had Millett K-frame revolver sights added and some parts were hardchromed. I also had the trigger narrowed and contoured to match that of the Pre-B CZ75 and the frame and slide reblued.
If you can get the gun "right," it would be a shooter and with its size and weight, it's a pussycat in 9mm.
Good luck.
Best.
