.22 Short / Long / Long Rifle (LR) .22 is one of the most common calibers out there on the market and for a good reason. The ammo is cheap, has virtually no recoil, significantly less noise (especially sub-sonic .22), and is widely used as a training round. .22 Short / Long / Long Rifle are all rimfire cartridges, meaning the firing pin strikes the rim of the cartridge rather than a centroid primer. .22 S/L/LR is not suitable for primary self-defense usage in my opinion. FN 5.7 (5.7x28mm) Fabrique National designed this cartridge for usage in their FN Five-Seven pistol and the P90 Sub-Machine Gun (or PS90 Semi-Auto in the Civilian Market). It has recoil on par with a .32 ACP, but the kinetic energy of a common 9mm Luger (9x19) cartridge. It's original design intent was a controllable, compact, and high velocity cartridge that could defeat body armor for usage by Law Enforcement and Military usage. Common civilian market ammunition does not have the same capability to defeat body armor. The round is a niche round that has some commercial availability, and is rather loud due to the ballistic crack. FN 5.7 is not suitable for primary self-defense usage in my opinion. .25 ACP .25 ACP is a small, pocket gun caliber that was widely used in years past. It has very little recoil, and is still commercially available. It's metric equivalent is 6.35mm Browning, which can sometimes be found on imported ammo. .25 ACP is not suitable for primary self-defense usage in my opinion. .32 ACP .32 ACP (Auto Colt Pistol) was another cartridge designed for small, compact handguns. It is basically a slightly larger version of .25 Auto, and as such has very little recoil. It's metric equivalent is 7.65mm Browning, which can be found on imported ammo. .32 ACP is not suitable for primary self-defense usage in my opinion. .32 S&W Long This cartridge has been around since the turn of the 20th century and was used in several older Colt and Smith & Wesson revolvers. It can still be found commercially, although it can be hard to find. It is very soft shooting, and can be fired in the new line of .327 Magnum revolvers. .32 S&W Long is not suitable for primary self-defense usage in my opinion. .32 H&R Magnum .32 H&R is an adaptation of the .32 S&W Long that can still be encountered today in some product lines. It is a soft shooting chambering that can be fired out of the new .327 Magnum revolvers as well as those marked .32 H&R Mag. 7.65x25mm Tokarev This is a unique round that was designed by the Soviets for usage in the TT-33 semi-auto pistol. It is a shouldered case round that produces considerable velocity and as a result, good kinetic energy. The round produces slightly less recoil than most 9mm Luger handguns, although it does produce considerably more noise and muzzle flash. Be aware that surplus ammo has a tendency to crack the case at the neck extending to the shoulder. .327 Federal Magnum .327 Fed Mag is relatively fresh to the market and boasts less recoil than a .357 Magnum, but with the same ballistic effectiveness. The round is commercially available, but supplies can be hard to locate. From personal experience the round has 80 - 90% of the recoil and pop of .357 Magnum. .38 Special .38 Special is a widely available round that is used almost exclusively in revolvers. It is a soft shooting, low pressure round that can be fired out of a .357 Magnum or .38 Special revolver. It can generally be found in higher pressure, higher powered loads which are designated +P (Extra Pressure) which add some noise and recoil. Note: Airweights, LCRs, and other ultra lightweight revolvers have considerably more felt recoil with this round due to their light weight. .380 ACP .380 ACP has had a great resurgence lately for usage in compact pocket carry guns like the Ruger LCP and Kel-Tec P3AT. In a full size gun the chambering has less recoil than it's bigger sibling, 9mm Luger, but in the compact frame guns it tends to be similar, if not exceedingly so. It is known in the metric world as 9mm Kurz, 9mm Browning, 9mm Court, or 9x17mm (Kurz meaning "Short" in German) because the case is 2mm shorter. 9x19mm Luger / Parabellum 9mm Luger / Parabellum is by far the most widely used cartridge in the world. It's recoil is really the intermediary of the pistol cartridge world. It is manageable by new and old shooter alike, and is commercially available everywhere. The round is offered in a +P, +P+, and even a sub-machine gun rated loading which increase the felt recoil and noise in kind. Note: 9mm NATO is a 124 gr. FMJ high pressure 9x19 cartridge designed for the Beretta M9 and other NATO service pistols. Check with your manufacturer before shooting this ammo as it is essentially +P. .357 Magnum .357 Magnum used to be the king of the hill in handheld firepower, but since the creation of .44 Magnum it has ellapsed into a role it fills well, self-defense. It is a moderate recoiling cartridge based off of an elongated .38 Special case that comes in a wide variety of loads, some of which have noticeably more recoil than standard commercial ammo. .38 Super .38 Super is a niche semi-auto caliber and is almost exclusively marked as +P. It is most commonly used in countries where military calibers are restricted, and in competition guns due to it's flat trajectory and it's larger case volume compared to 9mm Luger. Recoil is soft to moderate depending on the load. .357 Sig .357 Sig is a .40 S&W case necked down to accept a 9mm bullet. As a result of this shouldered case it produces significant amounts of pressure and velocity compared to 9mm Luger. The recoil is moderate, and it carries a loud muzzle report. It is widely used in the Law Enforcement community and to a lesser extent in the commercial market. .40 S&W .40 S&W came about via the LEO communities search for a replacement to the 10mm Auto cartridge. The .40 S&W is a 10mm Auto cut down with less powder charge, and thus greater controllability, but it maintained the overall effectiveness of the parent chambering. It is still widely used in the Law Enforcement community, and amongst the commercial market. Contrary to popular belief, the .40 S&W was not intended to be an intermediary cartridge between 9mm and .45, on the contrary it has slightly more felt recoil than both due to a combination of a heavy grain weight bullet and moderate pressure. It is available in a +P loading which does add noise and recoil. 10mm Auto 10mm is a moderate recoiling round that originally was popular with the Law Enforcement community, but has since became a cult classic amongst it's followers. It's commercial availability has dwindled in the past decade, but it has remained on the map. It is comparable to .357 Magnum in terms of versitility and loadings. .41 Remington Magnum .41 Rem Mag is a moderate recoiling cartridge that was developed to be the middle ground between .357 Mag and .44 Mag, and that role it did fill, but unfortunately it never really took off. Ammo is still commercially available for this cartridge. .44 Russian .44 Russian is the parent case to .44 Special, and the grandfather to the venerable .44 Magnum. It is a shorter case than both, and is soft shooting (comparable to .38 Spl.), especially in cowboy-action loads. It is still commercially available due to the usage of this cartridge in Cowboy-Action Shooting. .44 Special .44 Special is an elongated .44 Russian case which was developed to use, then modern, smokeless powder at the turn of the century. It also is commercially available as an alternative to .44 Rem Mag, and exhibits similarly soft recoil and ballistics as .44 Russian, ironically. .44 Remington Magnum .44 Rem Mag is a widely known caliber due to it's fame in Dirty Harry. It is a heavy recoiling cartridge that is used for personal defense from just about anything that breathes. There are many commercial loadings available on the market ranging from standard soft points to hollow points to hard-cast lead bear loads. The latter are +P+ rated and kick pretty damn hard. .45 ACP .45 Auto / ACP is a very popular cartridge with a heritage a mile long in the 20th Century. It was widely used in combat by American armed forces since the day of it's inception and continuing to this day. It is widely commercially available and can be found in +P loadings which increase the noise considerably (due to sonic threashold), and the felt recoil somewhat. The round itself is a soft to moderate recoiling round. .45 Colt (aka Long Colt) .45 Colt was the standard of the Cowboy era and remains a widely popular cartridge amongst Cowboy-Action shooters and Wild West lovers alike. Recoil is soft to moderate, comparable to .45 ACP in many regards. It is used in many commercially available single-action revolvers as well as the recent Taurus Judge. Ammo availability is pretty good, and there are a wide assortment of loadings. .454 Casull The .454 Casull is the .45 Colt case, strengthened, and pushed to the limit. It is a very heavy recoiling round that produces considerable amounts of kinetic energy, making it popular for hunting. The ammo is moderately available and generally oriented towards hunting loads. .460 S&W Magnum This is the big brother to the .454 Casull cartridge. Designed recently as a flatter shooting varient to the .500 S&W Magnum it is a VERY heavy recoiling round that can be used to hunt anything short of a tank. .500 S&W Magnum The current champion of the recoil throne. The round produces VERY heavy recoil. It is widely used for hunting and is oriented towards being a primary bear defense chambering. If you can't kill it with this or .460 S&W Magnum then I suggest running. Wildcat Calibers .357 Maximum, .375 SuperMag, .414 SuperMag, .445 SuperMag These were developed by the late Elgin Gates and all but the .375 are simply the Magnum case lengthened to 1.605". The .375 is a shortened .375 Winchester. Designed for extended frame revolvers, primarily the Dan Wesson SuperMag series, and the T/C Contender for silhouette competition, these cartridges are meant to launch heavy bullets at 200+ fps over Magnum velocities and serve equally well for hunting. Currently there are no production revolvers available in these calibers, but they remain available in the Contender.