.40 Smith & Wesson
The .40 S&W cartridge is a popular and relatively new round designed primarily as a more effective replacement for the 9mm round, which has been shown to lack sufficient stopping power according to some studies and real world events.
Appeal to Survivalists
The .40 S&W is popular among the prepared for several reasons. The first is that it offers greater stopping power than the 9mm, while maintaining more manageable recoil and a lower price than the .45 ACP. The second is that it is the standard issue round for many law enforcement agencies.