A check of several sources in my gunny-stuff library indicated it has a 4 1/4" barrel; several online sources seem to confirm it.
However, if you have the gun on-hand, you don't have to guess, you can just measure it yourself. You'll need something small enough to slip down the barrel and still stick out a bit (like a pen, non-sharpened pencil, or a cleaning rod), a felt-tip marker or piece of masking tape, and a ruler or other measuring device.
Make double-darn-sure the weapon is COMPLETELY unloaded, with no magazine in place. Close the slide, and slip the pen/pencil/rod down the barrel until it stops. Using the felt-tip marker or a piece of tape, mark a spot on the pen/pencil/rod that is even with the end of the barrel. Remove the pen/pencil/rod and measure from the end to the mark/tape; that is your barrel length.
Note: on an autoloading/automatic handgun, the chamber (where the cartridge is loaded to fire the weapon) is traditionally included when measuring the overall barrel length. In a revolver, the cartridges are loaded into the revolving cylinder, the length of which is NOT included with the barrel when measuring; so, to get a revolver's barrel length, just measure from the front of the closed cylinder to the end of the barrel.