
There are a lot of new gun owners coming into the mix lately, and if that’s you — Welcome!
But this whole thing can be daunting. There are a lot of terms that you should know, different things about your handgun that you have to figure out, and as I’m sure you’ve found out, going to the gun groups on Facebook can be disastrous for people with questions.
This blog post is meant to do one thing, get you up to speed on some of this more important stuff.
Let’s get started:
What is in battery?
When your gun is in battery, it basically means that it is ready to fire. It is the state of the gun when the slide has been racked, or a previous shot was fired, and is ready to fire with a round chambered in the gun.
When a gun is out of battery, it is the exact opposite.
What is trigger break?
The trigger break is a term used to describe when the trigger reaches the point where it releases the firing mechanism, causing the gun to fire, or click in dry fire practice.
What does ACP mean?
ACP is an acronym that stands for “Automatic Colt Pistol” or “Auto Colt Pistol.” It is essentially a couple of different pistol cartridges developed by one of the greatest minds in firearm inventing, John Moses Browning.
Browning made cartridges like the 45 ACP and the 380 ACP, two of the most popular handgun cartridges around today.
What is semi-automatic?

Semi-automatic is speaking about the operation of the firearm itself, or how the gun operates when the trigger is pulled. In terms of handguns, they usually tend to either be semi-auto, revolver, and rarely other types like single-shot break actions.
A semi-auto pistol is essentially a magazine-fed handgun that automatically loads the next round into the chamber, based only on the action of the gun after fired. A semi-auto will fire one round per trigger pull and is not to be confused with automatic.
An automatic gun is one where the trigger is pulled and fires for as long as it is held or the gun runs out of ammo.
What is Double Action Only?
A double action only, or DAO handgun is one that utilizes a hammer that is connected to the operation of the trigger. As the trigger is pulled to the rear of the gun, the hammer begins to raise up off of the part that it was laying on.
After the trigger and hammer reach a certain, pre-determined point in the operation, the trigger “breaks” (see above), and the hammer drops on the firing pin, starting the shooting cycle.
Double action only can be either a revolver or a semi-automatic handgun, but the hammer isn’t always visible.

Double action guns tend to have a long, hard, heavy trigger pull that requires the intent of the operator in order to pull.
What is Single Action Only?
A Single Action Only, or SAO, is a handgun where the firing mechanism and the trigger are independent of each other in that the hammer or striker is already in position (they are obviously still connected though).
Either older style revolvers and some modern semi-auto guns can be found in SAO.
A single action gun usually has a lighter, crisp trigger that is easy to pull (this is not always the case, however).
What is striker fired?

A striker fired handgun is one that utilizes a striker, sort of like a firing pin, instead of a hammer. The striker is an internal part within the slide.
The striker is usually actuated by pulling the slide back and releasing it into battery (see above). The round is fired when the trigger is pulled, breaks, and sends the striker forward to hit the cartridge’s primer.
What is hammer fired?

A hammer fired handgun is one that utilizes a traditional hammer to fire the gun. The hammer can be either internal or external, but they function the same, with the exception that the internal hammer cannot be set by the person.
The hammer can either be actuated by the operator or by the action of the firearm itself, or both depending on if it is a DA/SA gun (see below).
The hammer fires the shot off once the trigger reaches the point of break, sending the hammer into the cartridge’s primer.
What is DA/SA?
A DA/SA gun is also known as double action / single action. Basically this is a gun like the Beretta 92 where the first shot is in double action, and the subsequent, follow up shots, are in single action.
The first shot is a long, heavy pull and the subsequent shots are short, easy pulls.
What is a center fire handgun cartridge?

A center fire handgun cartridge is one that utilizes either a boxer or berdan primer in order to ignite the gun powder on the inside of the case.
It is a center fire because the primer sits in the center of the backside of the casing.
Centerfire cartridges are the most modern handgun cartridges available and are the most consistent in firing, with the boxer-primed cartridges being the best.
What is a rimfire handgun cartridge?
A rimfire handgun cartridge is one where the entire case is one piece, with no additional primer on the outside (as mentioned above). Instead, these cases are primed on the rim.
This means that the ignition of the primer happens when a hammer or striker hits the rim of the case. The most popular rimfire case is 22 long rifle, or 22lr.
What is a rimmed cartridge?

A rimmed case is one where at the base of the casing, there is a rim that sticks out past the rest of the cartridge. Examples of rimmed cartridges are 357 Magnum, 38 Special, 44 Magnum, 44 Special, etc.
Rimmed cartridges are popular for revolvers and lever actions and are considered old, but reliable technology. There are some semi-auto handguns that have utilized firing rimmed cartridges, but not many.
What is a rimless cartridge?
A rimless cartridge is a more modern approach to extracting the cartridge case. There is still a partial rim present for the extractor to grab onto, but it is flush with the rest of the cartridge.
See the above picture.
Read Next, more from the “things you need to know” series:
Things you need to know about the AR-15.
Things you need to know about revolvers.