Semi-Automatic, Revolver, Caliber, Cartridges: What You Need to Know When Buying a Gun

What do you really need to know before buying a gun? Last week, in the first installment of our series, we talked about some of the things you needed to think about, like how you plan to be using it and some basic definitions. But there’s a lot more to buying a gun that will work well for you than understanding what the words mean.

So, let’s move on to Part 2 of our Monday GunDay guest series by Steve Candidus, who has generously written these articles to make choosing a firearm easier.

What You Need to Know When Buying a Gun

By Steve Candidus

Revolvers vs. Semi-Automatics

Let’s start with an important note – your ammunition is not called bullets – that is what exits the barrel. The complete bullet, powder, and brass or aluminum case, is called a cartridge or round.


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A revolver, sometimes called a wheel gun, has a cylinder typically holding five or six rounds. A semi-automatic is flatter in profile and typically holds more ammunition.  It fires a bullet each time the trigger is pulled, and extracts and ejects the spent cartridge case from the firing chamber, re-cocks the firing mechanism, and loads a new cartridge into the firing chamber.

Revolvers do not come with a safety. The trigger pull is longer and it takes more effort to fire them and thus acts as a safety – sort of. Revolvers come in sizes ranging from small pocket size guns to large heavy hunting guns. They are a good choice for home defense as their extra weight is actually an advantage. The weight absorbs more of the felt recoil.

They are loaded by releasing the cylinder button to the rear of the cylinder and swinging the cylinder out exposing the cartridges. By pushing on the cylinder rod that is located under the barrel when closed and in the center of the cylinder the rounds will be pushed out.

Cylinders can be reloaded either one at a time or with gadgets called speed loaders. These are plastic devices in the exact dimension of the cartridges in the cylinder and are held in place internally by small clips. By simply dropping the rounds into the cylinder and releasing the hold mechanism (a twist or a push) the entire cylinder is loaded very quickly.


Semi-Automatics, referred to as semi-autos, are thinner in profile and often carry more ammunition than revolvers.

Note that although some refer to them as ‘autos’ they are still not what is called ‘fully automatic’. A fully automatic weapon is classified as a machine gun. Assault weapons fall into this category and regardless of what you may hear or read in the news media, neither is easily accessible to the general public. These types of weapons require only one pull of the trigger to fire all of the rounds that the gun carries. We will not be discussing those types of guns here.

A semi-auto will only fire one bullet with each pull of the trigger.

Ammunition in a semi-automatic is contained in what’s called a magazine. It is a long rectangular enclosure that can be easily inserted and replaced for a quick reload for the gun. The magazine is located inside of the grip and will drop down to remove by pushing a magazine release button located just behind the trigger on the grip. To insert a new one, just push it in until it clicks.

A semi-auto with all of the rounds in the magazine in a single line is called a single stack. Those with alternating lines of ammo are called a double stack. Typically, a gun that will hold eight rounds in a single stack model will hold about fourteen or fifteen when designed as a double stack. These single stack/double stack magazines are not interchangeable. They are specific to the particular gun they were designed for.

Single stack semi-autos are smaller, lighter, thinner, and are usually more comfortable for smaller hands. They are also easier to conceal. You might consider a single stack auto in warm weather when wearing light clothing and a double stack in colder weather with heavier clothing.

Semi-Automatics come with a variety of different types of safety mechanisms called safeties. A passive safety is one that the shooter does not have to activate to set as on or off. The most common type of these look like a split trigger. One part is the firing mechanism and the other is the safety. When you place your finger on the trigger, it will automatically release the safety.

Some semi-autos also come with a grip safety. With a grip safety, the gun is set to safe until you hold it in your hand. That pushes the safety in and to the fire position.

There is also a manual safety on some semi-autos. These are usually located on the slide (that’s the part that moves) and offer an additional measure of safety at the expense of an extra motion that you must remember to initiate before firing.

Regardless of what you ultimately choose, the most important safety on your gun is to remember to NEVER put your index finger on the trigger until you are ready to fire the weapon!!! You might have seen some photos of someone holding a gun with their index finger alongside the barrel. That is where it should be until the exact moment that you intend to fire it.

Lastly, one of the topics that you might hear discussed is whether or not a particular auto has a firing pin. It might seem odd to someone not familiar with guns, but not all guns do. A company called Glock pioneered semi-autos with what are called strikers. They are a simple device and are very reliable. A firing pin is more complex. Both work equally well and your decision need not be based on one or the other. It is simply how the manufacturer designed them so don’t be intimidated by a highly knowledgeable gun person bringing them up. As the shooter you are indifferent.

Metal vs. Polymer

This refers to the material that most of the gun is made of.

Polymer, sometimes referred to as plastic, is a very strong and very light material that is used in constructing the frame (the guns skeleton) and its outside covering. Polymer guns are currently the most popular and because they are made from a mold rather than machined, they can be made with a comfortable and ergonomic grip.

Most polymer guns use a striker mechanism rather than a firing pin (see part 3 Revolvers vs. autos). In order to know whether your auto has a striker or a firing pin you can insert a pencil – eraser end first – into the barrel (making sure that the gun is unloaded first) and pull the trigger. If the pencil shoots up and sometimes even out it has a firing pin. If it barely moves, it has a striker.

Metal guns have an all-metal frame. Some use an aluminum alloy rather than steel to reduce weight, but all will usually be heavier than polymer guns.

The reason that there are more options available for you today for polymer guns than for metal guns is partly because they are lighter, but mostly because they are far less costly to manufacture. For a gun manufacturer, making a polymer gun from a mold is a lot less costly than machining one out of metal.

The barrel and the slide (the top part that moves backward when fired on semi-autos) on all semi-automatics are metal.

Revolvers are usually metal and heavier than semi-automatics.

All About Caliber

Caliber refers to the diameter of the bullet that exits the barrel. It can be a bit confusing too.

For instance, a .45ACP (auto) bullet has a diameter of .451 inches. A .357 magnum has a diameter of .357 inches, but so does a .38 caliber. A 9mm bullet has a diameter of 9.01mm or .355 inches, but so does a .380 auto.

The weight of the bullet is expressed in grains. For instance, a 9mm 115g means that the bullet is 9mm in diameter and it weighs 115 grains.

For personal defense, whether home or carry, the all-time king for stopping power is the .357 magnum. It is only available in revolvers but has the best record of stopping an assailant and in doing so quickly.

Any revolver that is chambered (designed) for .357 magnum will also shoot .38 specials safely. It is not true the other way around. You can NOT fire a .357 magnum round in a gun chambered for .38 special. First of all, it likely will not fit in the cylinder, but a .357 magnum has a lot more energy and would likely damage both the gun and hurt the shooter if they fired a .357 magnum in it.

The same is true for .44 special and .44 magnum.

If you chose a revolver a .357 magnum is a good choice and it can be loaded with the lesser recoiling, but still effective .38 specials or even .38 special +P’s if you can handle the increased recoil.

A ‘+P’ designation means that it is loaded to a higher power level than the standard non +P cartridge with the expected better stopping power and higher recoil.

.44 special and .44 magnum would likely not be a good choice for a new shooter as the weight of the gun and the recoil would both be high.

A few years ago, a new cartridge called .327 Federal magnum was introduced. It has much better stopping power than a .32 auto and has about 25% less felt recoil than its big brother the .357 magnum. It is a very good choice for the beginner that wants to use a revolver. I wish there were more gun choices for them.

For semi-autos, the .45 auto is arguably the king. I say arguably because the full power 10mm semi-auto (.400 inches) is right up there with it albeit with a bit snappier recoil. The tradeoff here is that you usually get at least one extra round of 10mm and better penetration to boot. The 10mm is more like a .357 magnum in a semi-automatic, but its recoil is difficult for the beginner to handle. Smith & Wesson makes a little brother called, not surprisingly, the .40S&W. It is very popular with police departments in the US and is a good choice for personal defense.

The most popular cartridge for automatic handguns is the 9mm. It is sometimes called 9mm Lugar or 9X19. The 19 refers to its case being 19mm long.

It’s the most popular handgun caliber in the world. Ammo is cheap, plentiful and available everywhere and there is probably a larger selection of handguns in 9mm than any other.

If you are planning on a lightweight handgun 115 grain HP’s are a good choice. The best option with a slightly heavier gun or if recoil is not the limiting factor then 124 grain +P’s are best.

The 9mm is not as powerful as the 40S&W or .45ACP, but the same size gun can hold more rounds and its power is more than adequate.

The smallest caliber that should be considered for autos is the .380ACP. Like the 10mm vs 40S&W, it’s the little brother to the 9mm. Note that its stopping power is marginal and many of the guns available for this caliber are not very reliable. That’s not a good thing for a weapon that you might have to depend on for your life, but if that is what you comfortable with and you have a gun that shoots it reliably go for it.

In a pinch, even a 22LR will do. They are small, economic, and recoil is very light. Although dismissed as ‘mouse guns’, don’t dismiss the .22LR. They are used commonly by some of the world’s spy agencies like the Israeli Mossad. You can carry one in an ankle holster or in a purse and hardly even notice that you are carrying it.

Remember that the ‘mouse’ gun that you have with when you need it is 100% more effective than the portable cannon that you left at home because it was too heavy to carry around all the time.

Whatever caliber you ultimately decide on, aside from the safety slugs mentioned earlier for home defense, hollow point bullets are best for self-defense.

How Weight Affects Recoil

Although weight is not an issue with a gun for home defense, it is a big issue for something that you intend to carry all day and perhaps every day.

Remember when looking at the weight of the gun that you also have to factor in the weight of the ammunition. The total weight is what you need to consider.

As with the caliber selection where the more powerful the caliber the greater the recoil, the lighter the gun the greater the recoil will be.

It goes back to Isaac Newton’s law that every action has an equal and opposite reaction.

Polymer guns are inherently light and although seemingly attractive for carrying, they will also yield a stronger felt recoil. The better ergonomics that can be built into them due to ease of manufacturing them with complex contours versus metal guns helps some, but the laws of physics are not to be denied. The lighter the gun the greater the recoil.

An all steel gun will weigh the most and with the same caliber will have the least recoil. Metal alloy guns (steel slide and barrel with an aluminum frame) weigh less and recoil a little more. The new exotic metal (titanium) guns are lighter still but will have the greatest recoil of all metal guns.

Polymer is lighter than metal and felt recoil will be higher.

You will need to find the best compromise of weight versus recoil. It is different for everyone. It will also vary by experience. The more you shoot the more you will become comfortable with recoil.

Find a balance between the most powerful caliber that you can comfortably handle and the highest weight gun that you want to carry.

Anything to add? Any questions?

This is the basic information you’ll need when buying a gun, but no amount of textbook knowledge can take the place of experience.

Before buying a gun, the most important advice I can give you is to find an instructor who will let you test a variety of guns. My gun store allows you to test different models but they charge you about $10 per gun to shoot five rounds through. It’s worth it, though, to make sure you like and are comfortable with the firearm you are about to purchase. Would you buy a car without a test drive? The same philosophy should also hold true when buying a gun.

For example, my former instructor and good friend carries an M&P Shield. It’s her favorite gun and she was convinced I’d love it, too. When I shot it I felt like I couldn’t hit the broad side of a barn and couldn’t wait to go back to my Glock.

Reprinted with permission from The Organic Prepper.