I'd suggest you purchase some of the Snap Caps to use while Dry Firing. I like the A Zoom ones that are out there. You can also use these to practice loading and unloading - something you should practice, too.
I also use these during training sessions to see if a student is 'jerking' the trigger. I'll load up the gun with one of more of these Snap Caps and if the person is 'jerking' it will be very clear when they hit one of these "Blanks".
I use snapcaps in my other semi auto's, but not my 3913. Why? After 3 or 4 strikes, the snap cap is lodged in the barrel. They were A-Zoom snapcaps and it continued to happen even after I sent it to S&W for a checkup. I literally had to wrench the slide back to remove it. Can't be good for the extractor.
The only downside to dry firing without snap caps is that after quite a lot of dry firing, the firing pin spring can fatigue and break. The spring is easy to replace and is cheap; curiously, the gun functions in an apparently normal manner for quite some time after the spring fails. Only when the pieces 'wind up' inside each other do you start to notice a sluggish retraction. The problem with 'A-Zoom' caps is that the rim is thinner than normal - the red plastic ones with the brass bases (sold under several brand names) seem to have rims of normal thickness and do not 'migrate' into the throat.
I have contacted S&W customer service and received two answers yes and no. SO I have just gone with the aluminum A-zoom caps. They also work well for malfunction drills.
A: Yes, except for the .22 caliber pistols which includes models 22A, 22S, 422, 2206, 2214, 2213 and 41. .22 caliber revolvers such as models 17, 43, 63, 317 and 617 also should not be dry fired.
Q: Why can't I dry fire my .22 pistol or revolver?
A: Dry firing a S&W .22 pistol or revolver will cause damage to the firing pin.
If one reloads it is easy to make a snap cap
that will hold up longer than the store bought ones.. Make a dummy round and fill the primer pocket with some hard but not too hard stuff..
Hot glue from a glue gun would work and can be replaced when needed..