There have been literally thousands of different gun models, but The Evolution of the Handgun infographic from GunVault.com covers most of the major advancements in handgun design.
I really like the first two sections of this design, and I think the last section was unnecessary. The timeline and the gun specifications sections do a good job of laying out the data and keeping it simple. The barrel length and the calibers of each model work very nicely. Since the # of Rounds data is quantitative, I would suggest visualizing that as a series of circles instead of a solid bar to better communicate quantity.
The last section adds a lot of text, repeats the data from the second section and makes the overall infographic gratuitously long. The flags showing the country of origin could easily have been added to the earlier sections.
Thanks to Archie for sending in the link!