I give up! Is it a revolver, a pistol, or a handgun?
This is a point of confusion for a lot of inexperienced writers (i.e. ones who have not been barraged by gillions of critical e-mails). The terms “pistol” and “handgun” are basically interchangeable as they define a firearm designed to be shot with one hand, as opposed to being fired from the shoulder. Some experts further sub-classify pistol as a firearm whose chamber is integral with the barrel, (thus distinguishing it from a revolver) but for our purposes I think either would be fine. The term “revolver” describes a particular “action” wherein the chambers are part of a revolving cylinder, but it too can be called a pistol.
It bears mentioning that very few American law enforcement agencies allow their officers to carry a revolver as a primary duty weapon. Most require a semi-automatic handgun for their officers. Some agencies even require their officers to carry the same make and caliber so their ammunition is interchangeable. Almost all agencies will have an “approved” list of acceptable makes, models, and calibers.
While the above terms are interchangeable I would suggest that you pick one and stick with it. Obviously, if a character has a revolver then you need to make that clear. Pay particular attention to the ammunition capacity. Nothing bothers a reader more than a gunfight in which a character shoots nine shots from a six shot revolver without re-loading. It’s always best to select a particular model and caliber and then study the specifications. In the best case scenario you might be able to test fire one at a gun range so that you understand its functions. Remember; never shoot a firearm without proper training and or supervision by someone familiar with the weapon.