Guess the caliber!
Nope, hint. S&W series, starting with 6XX
357/38 which is the same as a 9mm
Umm, I won't put a 9mm round in my 686+. (And, I won't put a .357 magnum round in ANY of my 9mm guns). Not that they'd fit. Check out the diameters of the various 9mm bullets and 38 spcl. or .357 magnum rounds
A Smith 6XX will use a .357" bullet (.358" cast). 9mm uses a .355" (.356" cast).
Yeah I wouldn't swap 9mm cartridges with 357/38 either just they use the same bullets as does the 357 Sig which is a .355-.358 bullet in a necked down 40 SW case
Or it could be a 625, taking 45ACP or 45 Long Colt. Which is what I took this picture of.