The way I remember it from the Bond books I read in the 1960s was that in "From Russia with Love," his Beretta .25 caught on his clothes and malfunctioned when he tried to shot the Soviet woman with the poison-tipped blade in her shoe.

In the next book, "Dr. No," Bond had been ordered to upgun. The armorer Q gave him a choice of a J frame S&W or a Walther PPK, probably in .32 ACP. Bond carries the Smith on his mission but loses it in combat. Thereafter he uses the Walther.

As I was typing this, I did a quick search to check my memory and found this very interesting site about the guns of 007.

The Handguns of Ian Fleming?s James Bond