While I was not a spy, I was a USAF fighter pilot. When in compbat I carried an issued S&W Combat Masterpiece .38spcl.
On non combat missions I carred a .22lr revolver for survival purposes. I also carried it hiking and hunting. Got several grouse and rabbits with it. The advantage of the .22 is that you can carry a lot of ammunition for an accurate pistol to bag food in a survival situation. I seriously doubt that there was any intention for Gary Powers to fight with the .22.
Having said that, I agree with the thread that most writers are IGNORANT about guns. But then you just have to suspend reality a bit and live in the fiction you are enjoying.
Cogito, ergo armatum sum