What is the modern handgun? Why is this piece of crafted metal and (recently) hard plastics still in great demand not only in military forces and police departments ALL around the world? The answers are: They are small, lightweight (well, most of them :-) and provide good firepower; suitable, not only for defensive situations, but for offensive ones, and even for medium game hunting. Of course, for each situation, careful choice of the proper handgun AND ammunition must be made. Handguns are divided into a few classes: semi-autos (or pistols), revolvers, and non-autos (single or multibarreled, single-shot or magazine fed).
Semi-autos use part of the energy produced by burning cartridge powder to remove the used cartridge from the chamber, cock the hammer (or striker) and load a new cartridge in the chamber, so the pistol will be ready for the next shot. Cartridges are usually fed from a box magazine, located in the pistol's handle. Box magazines may contain up to 15 cartridges (or more) in single or double columns, depending on the pistol model, and are easy (and very quick) to reload.
Revolvers got their name from the rotating (or Revolving) cylinder, which contains cartridges. Usually the cylinder holds from 5 to 7 loads, although some .22 caliber revolvers may contain up to 8-10 cartridges. Loads in the cylinder may be reloaded in 2 ways (depending on revolver design) - one by one, as, for example, the Colt PeaceKeeper does (and almost all old-timers), or all simulateounosly - when the cylinder is switched to the side or when the is frame "broke open." Both revolvers and semi-autos have two main "action styles": Single action and Double action.
Single Action means, that the Revolver must be manually cocked (and, thus, the cylinder is rotated to the next cartridge) for each shot. This mode was the only one available in all old-time revolvers (such as the Peacekeeper), and is still available in most double-action revolvers. This mode improves accuracy but slows the fire rate. For Semi-autos, Single Action means that the pistol must be manually cocked for the first shot (usually, this is done by pulling the slide - this action cocks the hammer and feeds a cartridge into the chamber). For the second, and all consecutive shots, cocking is done automatically, when recoil force pulls back the slide.
Double Action for the Revolver means that the hammer for each (including the f irst) shot is cocked by trigger pull (this action also rotates the cylinder to the next position). This mode speeds up the firing rate and simplifies shooting actions, but greatly increases trigger pull (from 2.2-4.4 lbs usually found in single-actions, to 8.8-12.2 lbs in double-actions). For the Semi-autos, the hammer is usually cocked by trigger pull for the first shot only; the second and the rest are done in single-action mode. However, first load must be fed in the chamber by the slide pull. Some (most of them - compact) semi-autos and revolvers employ Double-action-only mode, which cocks the trigger for each shot, thus excluding single-action.
One of the biggest questions about handguns is: Why the Six-guns (a slang TERM for Revolvers) are stil alive when there's a big lot of the very reliable and larger capacity semi-auto handguns? The oldest answer is - reliability. Usually, given the same price (in low- or mid-range of prices), the revolvers were more reliable, primarily, because of the simplicity of the design. Today there's a lot of inexpensive semi-autos, that can hold twice or even triple as much loads ready to fire, than the common sixguns. But revolvers still alive. One of the main reasons to keep the revolver is that they're almost insencetive to ammunition. If your cartridge is capable of pushing a bullet thru the barrel of the sixgun - you got the working gun. No jams, no stoppages. Even in the case of the misfire you just got to pull the trigger again - and next round will go. In semi-auto, you need sufficient power to cycle the slide, thus rendering underpowered loads almost inoperable in semi-autos. Also, in case of the misfire, or jam, you should manually cycle the slide to fire the next round. In defensive scenario, this may cos you another second, and may be - your life. So, in general, sixguns are far less sensetive to ammo quality, and, due to simplicity and inherent design features, could withstand far more abuse. Also, when you go to the other, high-end of the loads (speaking in the terms of power), no semi-autos could withstand the power of loads such as .454casull or .475Linebaugh. Sixguns could.
Main drawbacks of the sixguns are small ammo capacity, slower reloading and bulkier size. While 6 rounds may be sufficient for self-defence scenarios, it may be really insufficient for the police or SpecOps actions. Also, replacing the magazine in semi-auto ususlly is much faster process than reloading a revolvers' drum. And, due to significant cylinder diameter, even the 5-shot revolvers are harder to carry concealed, than the modern compact handguns, while the latter could hold tvice as much cartridges.
Final selection of the guns is, undoubtfully, the owners' responcebility, but, in my opinion, revolvers are more suitable for civilians' self-defence and for hunting, while semi-autos are better combat and police guns.