How Do Double-Action and Semi-Automatic Pistols Differ?

How Do Double-Action and Semi-Automatic Pistols Differ?
By Ammunition Depot
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How Do Double-Action and Semi-Automatic Pistols Differ?

How Do Double-Action and Semi-Automatic Pistols Differ?

One of the things that throws people off when they become new gun owners and enter this world for the first time is the sheer volume of terminology. Terms like “double-action,” “striker-fired,” “semiautomatic” or even “ballistics” can all seem, frankly, like an alien language if you haven't been around guns before.

Naturally, we want to do everything we can as people who do know the meanings of these terms to be as welcoming to newcomers as possible. One of the best ways we can do that is by explaining the similarities and differences between certain terms, such as double-action and semi-automatic, as well as their histories.

So let's start there.

When Were Double-Action and Semi-Auto Invented?

Double-Action

The first double-action pistols were created in the mid-1800s, and the first double- action revolver was patented in 1856 by Lieutenant Frederick E. B. Beaumont, an engineer in the British Army.

His patent covered improvements to the existing Adams revolver, and the subsequent new design became called the Beaumont-Adams revolver. This revolver achieved great success in Europe and throughout the world — a patent was also granted to Beaumont in the United States. Many of the double-actions were licensed to be produced in Massachusetts, and a good number eventually saw action in the Civil War.

The first U.S.-made double-action revolver didn't come into being until about 20 years later, when Colt introduced the M1877.

While each of these was successful, they were early forerunners and not truly modern guns. It was Colt that introduced the first truly modern double-action revolver 12 years later with its M1889. The M1889 was the first revolver to have the swing-out cylinder as opposed to the older style top-break or side-loading cylinders.

Semi-Automatic

The first semi-automatic firearm in the world was a rifle developed in 1885. There were a few models of semi-automatic pistols that debuted within the years following the rifle; but it wasn't until 1896, when Paul Mauser introduced his Mauser C96 handgun, that the semi-automatic pistol really began to have some success. Mauser's gun, also called the "Broomhandle" pistol, opened doors for the semi-automatic pistols that followed.

However, there was another gun designer developing semi-automatic pistols in the same year as Mauser who provided us with what would eventually become our modern designs. That man was, of course, John Moses Browning.

Browning's first successful design was the M1900, which was developed with a 7.65mm cartridge. Browning then went on to create pistols in .25.38.380.45 ACP and eventually 9mm. Those last two cartridges reflect his most famous and enduring handgun designs: the 1911 and the Browning Hi-Power — perhaps you've heard of them? It is from those guns, one could argue, that most modern guns followed.

What Do Double-Action and Semi-Automatic Mean?

Both terms refer to specific functions of the firearm. More specifically, they refer to specific functions related to firing the firearm.

Double-Action

The term double-action refers to the operation of the trigger. A double-action handgun is one with a trigger that's designed to both cock the hammer of the gun and fire it.

In the early days of guns, many designs stayed with the form factor of the flintlock pistols, meaning the hammer had to be pulled back to fire them. This is what's commonly referred to as single-action. The double-action created a way for the single trigger pull to both cock the hammer and release it to shoot.

The “double” in the term double-action refers to the two things happening within the gun during the single act of pulling the trigger. The first is that it pulls the hammer back, and the second is that it fires the gun. If this gun is a revolver, the cylinder is also turned as the first action of cocking the hammer takes place.

Another interesting little tidbit about double-action guns is that some function as both double-action and single-action, and others are double-action only. These are often abbreviated as DA/SA for double-action/single-action and DAO for double-action only. Don't worry, we'll get to some examples in just a minute.

Semi-Automatic

The term semi-automatic refers to the operation of the entire gun itself. A semi-automatic gun is one that inserts a new round into the chamber after ejecting the one that has just been fired. It's any gun with the action that cycles through that motion.

What makes it semi-automatic (as opposed to just being an automatic) is that, after doing this cycle, the trigger must be reset. In order to fire another round, the trigger would need to be activated again, whereas with an automatic, the trigger can simply be held down. For a semi-automatic, each round fired must have its own trigger pull.

Crossover

This actually brings us to an interesting similarity. Even though they are referring to different things, both a double-action and a semi-automatic pistol will fire a round each time the trigger is pulled. In fact, there are some double-action pistols that are semi-automatic.

Any modern non-revolver gun that uses a hammer is going to be both semi-automatic and double-action. The Beretta 92, also known as the M9 because it was the standard sidearm of the U.S. Army, is a double-action hammer fired semi-automatic pistol. It's also an example of a DAO gun.

The much beloved 1911, the winner of two World Wars, one of the most famous guns of all time and the gun that the Beretta replaced, is actually a modified single-action pistol. While the semi-automatic action of the pistol cocks the hammer back as it goes through its cycle, the hammer must actually be pulled back manually to fire the first round that's chambered. Or, at least, this was the case originally; there are now modern versions that are double-action.

However, just because a modern gun is semi-automatic doesn't mean that it's a double-action — a double-action gun must have a hammer. There are some very popular modern pistols that are semi-automatic and don't use a hammer; instead, they use a striker. You may have heard of some of them: the Sig Sauer P320, the HK VP9 and literally every Glock.

Some guns, like the Sig Sauer P229, are a DA/SA type of gun that is also semi-automatic. When loading a gun such as this, you can rack the slide to simultaneously chamber a round and cock the hammer, resulting in it functioning like a single-action.

Alternatively, you could always use the built-in decocker to lower the hammer without firing it, and then pull the trigger to have it operate as a double-action. Then, after it's fired, the semi-automatic action cocks the hammer once again.

Differences between Double-Action and Semi-Automatic Guns

The biggest difference between double-action and semi-automatic is these terms refer to completely different operations; that is, they’re not mutually exclusive. “Double-action” refers to the action of the gun or, more specifically, what happens when the trigger is pulled. “Semi-automatic,” on the other hand, refers to what happens when the gun engages in its cycle of fire — the operation of the gun as a whole, not just the trigger.

Learning all of the technology and terminology that goes along with being a gun owner is a never-ending process. Hopefully, this helped clear things up a bit and now you're better able to distinguish between double-action and semi-automatic handguns.

7 months ago
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