What is a Bolt Carrier Group (BCG)?

The AR-15 has a locking rotating bolt design, and the Bolt carrier group is perhaps the most important part of the rifle. The BCG, or Bolt carrier group is that actual part of the rifle that fires the round, apart from that the Bolt carrier group in an AR-15 serves the following purposes.

  • It contains the firing pin, which ignites the primer of the bullet and fires it.
  • It ejects the spent casing of the fired bullet
  • It loads a fresh round into the chamber
  • It recocks the hammer in the lower receiver, allowing the new round to be fired.

How does the Bolt Carrier Group work in an AR-15?

Now that we know what the bolt carrier group is supposed to do, let’s talk about how it does it. The BCG relies on the gases created by the fired bullet to operate. The gas travels from the barrel, through the gas tube, and reaches the bolt carrier key or gas key. This unlocks the bolt, and the gasses hit the bolt, moving it backward.

On the way back, the extractor takes the spent casing out of the chamber, and a spring-loaded ejector forces it out of the receiver. The hammer is also recocked after the round is ejected.

The bolt moves back into the buffer tube, where the buffer spring compresses. As it decompresses the bolt moves back forward, picking up another round from the magazine and chambering it. The bolt rotates to lock, and the rifle is ready to fire the next round.

The BCG keeps going through these steps with every round that is fired.

What are the parts of the Bolt carrier group?

Bolt Carrier:

The bolt carrier is like the primary housing that holds all the other components of the bolt carrier group. The carrier key or the gas key is also attached to the bolt carrier.


The AR-15 has a rotating bolt, which has locking lugs on it. The bolt rotates about 15 degrees and locks into the chamber. Then the bullet is fired, the bolt has to absorb the initial explosion, and keep it in the chamber. Therefore, bolts are made from forged steel.

Firing pin:

The firing pin rests inside the bolt. When you pull the trigger, the hammer falls on the firing pin, which strikes the primer of the bullet, and ignites it, firing the projectile through the barrel.  There is also a retaining pin with the firing pin, which keeps it in the bolt.

Cam pin:

The job of the Cam pin is to prevent the bolt from over-rotating when it unlocks because of the gas pressure.


The extractor takes the spent casing of the fired round out of the chamber. It hooks the rim of the round, and as the bolt moves back, the round is also extracted.


The spring-loaded ejector is located on the side of the firing pin. It maintains pressure on the round, and as soot at it is completely extracted, the ejector sends the spent casing flying out of the receiver


What are the Parts of an AR-15?

AR-15 style rifles are the most common rifles in the US, and one of the main reasons for this popularity and the rifle’s military adaptation and ease of maintenance. The AR platform rifles are very maintainable, and their parts are widely available. In fact, anyone with little knowledge could build an AR-15 at home using a parts kit.

If you want to do the same, or simply learn more about this incredible rifle, you need to know about all the parts that make an AR-15. So, let’s get into it.

The constriction of an AR-15 can be divided into three sections, the front, the receiver, and the buttstock. Here is an explanation of all the parts in each of these sections.

The Front:

Starting from the front of the gun, the first thing you will find is the muzzle device. Different devices like Compensators, Flash hiders, and suppressors can be installed on the Muzzle on an AR. Compensators help decrease muzzle rise, flash hiders eliminate the flash of the rifle firing, and suppressors decrease the sound of the gun.

Moving back, the next thing you’ll find is the barrel of the rifle, which is mostly made from stainless steel and can vary in length, however, it has to be at least 16 inches according to the Law in the US.

The barrel is covered with the handguard, which is usually made of polymers and has Picinati rails or M-Lok to mount accessories. The handguard also houses the gas block and gas tube. The AR-15 and other similar rifles are gas-operated, which means that when a round is fired, some of the gas from the barrel is redirected to the bolt carrier group, which moves backward due to the gas pressure, ejecting the fired casing, and on its way back chambers another round. This is what makes the AR-15 semi-automatic, or in the case of the M4 or M16, automatic.

The Receiver:

The receiver can be divided into two sections, the upper receiver and the lower receiver. The upper receiver of the AR-15 contains the bolt carrier group, charging handle, forward assist, and rear sights. The bolt carrier group is made up of several smaller parts, including the firing pin, the extractor, bolt, cam pin, and the gas key. Combined, all of these parts are responsible for loading your rifle after it is fired. The bolt moves back into the buffer tube after a bullet is fired, extracts the spent casing while moving back, and loads a new round coming forward.

The charging handle is a part of the upper receiver, which is used to manually cycle the bolt to load the rifle and the forward assist is there to improve reliability. If the bolt isn’t closing completely for some reason, the forward assist can help you close it.

The lower receiver contains the trigger group, magazine well, magazine catch and release, the safety selector, and bolt release. The trigger group consists of the hammer and the trigger, pulling the trigger releases the hammer, which hits the firing pin, and ignites the primer of the round.

The magazine well holds the magazine and the magazine catch keeps it in place. The safety selector is self-explanatory, it either blocks the trigger or allows you to shoot depending on its position. In M4s, the safety selector also has a full-auto option.

The AR-15 has a last round bolt hold open, so after a magazine is emptied, and you enter a new one, you don’t need to rack the charging handle every time, and can instead press the bolt release to allow the bolt to come forward, and have your rifle ready to fire.

The Buttstock:

The only functional part of the buttstock is the Buffer Tube. When the bolt moves backward, it has to go somewhere, so it goes into the buffer tube, which also has a recoil spring in it to absorb some of the recoils of the gun.

So, these are the parts that make up the amazing and super popular AR-15 rifle.

What Trigger Group is Best for My Build?

The trigger group is one of the most influential parts of your AR-15 when it comes to accuracy and weapon performance. There are loads of aftermarket triggers in the market, which have different pros and cons, and deciding which one is ideal for you can be a little challenging.

Your ideal trigger depends upon a lot of factors, and how you tend to use your rifle. Moreover, personal preferences also need to be considered to make sure that you get the best trigger group for you.

Here are some things you need to consider to find the best trigger group.

Single-stage Vs Dual Stage triggers.

In simple words, a dual-stage trigger fires in two stages. When you start pulling the trigger, the first stage has a stronger trigger pull, then you enter an intermediate area with a very slight resistance to pull the trigger. Single-stage triggers are a lot faster than dual-stage since they don’t have that intermediate area.

According to experts, dual-stage triggers are better for long-range accuracy, whereas single-stage triggers are better for close-up action, where you need to fire multiple shots quickly.

So, that is something you need to consider. If you are doing some long-range target shooting, then a dual-stage trigger would be better, but for competition shooting, where you need to land quick shots, a single-stage trigger is better.

Trigger weight:

The next important factor to consider is trigger weight. This is the amount of force it requires for you to pull the trigger until the hammer falls and fires the gun.

When it comes to competitive shooting, lighter triggers are the best. Match grade triggers are light and crisp, which means that there is almost no play in the trigger, and it fires with a very small force.

On the other hand, when it comes to self-defense, and actual close-quarters combat, light triggers aren’t the best option. Lighter triggers are easier to accidentally fire when moving around. This is why most mil-spec AR-15s and M4s have heavier triggers, typically around 6.5 pounds. On the other hand, competition triggers can be as light as 2 pounds.

However, longer triggers aren’t particularly great for accuracy, since they cause the shooter to anticipate the recoil, which can cause them to flinch, and take the rifle off sight. Some people use longer triggers, and press them near the breaking point until they are ready to shoot when they pull the trigger completely. Though this can be effective, it requires a lot of practice, and only a trained marksperson can do it right.

So, if you are a competition shooter, a light trigger group is best for you, and if you are using your rifle for home defense, or combat, a heavier trigger pull is the better option. A 4 lbs trigger is a good middle-ground for an all-purpose rifle.

Curved Vs Flat triggers:

Some trigger groups have standard curved triggers like seen on most rifles, and AR-15s, however, some people also prefer flat triggers. Neither has any significant tactical advantage or disadvantages, at the end of the day it does come down to preference, and whichever trigger feels better in your hand.



What is a Charging Handle?

Every semi-automatic rifle needs to be loaded, and the chagrin handle plays a very important role. The charging handle manually charges or loads the rifle, cocks the hammer, and gets the rifle in the ready position, hence it is called the charging handle.

Charging handles come in different sizes and shapes on different firearms. In some rifles, like the AK, the charging handle is an integrated part of the bolt carrier, and hence it moves back and forth with it. Such charging handles are called reciprocation handles. In other rifles, like the AR-15, the charging handle is non-reciprocating, which means it does not move with the bolt.

In the AR-15, the charging handle is located in the back, above the buffer tube, and under the rear sight block. It is a T-shaped handle, and when it is pulled, it brings the bolt back with it, against the tension of the recoil spring in the buffer tube.

When the charging handle cant be pulled anymore, you release it, and it allows the bolt to move forward, picking up a round from the magazine, and chambering it.

When do you need to use the charging handle?

The charging handle on an AR-15 serves many purposes. The AR-15 is a self-loading rifle, still, when you load a magazine, you need to charge the bolt manually so that the first round can go into the chamber. After that, all the rounds are loaded by the operation of the bolt.

The charging handle is also used to clear malfunctions and stoppages. For instance, if you have a bad round in the chamber that won’t fire, you can manually load another one using the chagrin handle. Other stoppages like failure to feed can also be cleared by pulling the charging handle.

You can also use the chagrin handle to make sure that the rifle is clear when you are cleaning or maintaining it indoors.

Why would you need an upgraded charging handle?

Most AR-15s come with mil-spec charging handles, which are usually right-handed. These charging handles are ideal for any normal shooter, but in some cases, competition shooters, or AR enthusiasts like to get aftermarket charging handles.

Some left-handed people also need to change their charging handles, or they can also opt for competition ambidextrous charging handles

Most competition shooters, and tactical enthusiasts who train with their AR-15s, opt for extender AR charging handles. These charging handles have an extended latch, which is easier to grab in the dark, or when you are wearing gloves.

Though the standard mil-spec charging handles aren’t bad at all, one of the best things about the AR platform is that there is an incredible aftermarket for its parts, and you can get some really good charging handles if you want.

Special: 10% OFF Black Friday Sale

We are running a Black Friday sale through the end of day on December 2nd at Tactical Transition! You’ll see some amazing deals posted throughout the site and none of which include the 10% off.. until you apply the code at checkout. Just enter BLACK10 on the checkout page and you’ll have the 10% discount applied. If you have any questions, feel free to shoot us a message on our contact page.

Valid til: December 1st, 2020

Code: BLACK10

Special: 10% OFF Labor Day Sale

We are running a Labor Day sale through the end of day on September 7th at Tactical Transition! You’ll see some amazing deals posted throughout the site and none of which include the 10% off.. until you apply the code at checkout. Just enter LD10 on the checkout page and you’ll have the 10% discount applied. If you have any questions, feel free to shoot us a message on our contact page.

Valid til: September 7th, 2020

Code: LD10

Special: 10% OFF Memorial Day Sale

We are running a Memorial Day sale through the end of day on May 27th at Tactical Transition! You’ll see some amazing deals posted throughout the site and none of which include the 20% off.. until you apply the code at checkout. Just enter MD10 on the checkout page and you’ll have the 10% discount applied. If you have any questions, feel free to shoot us a message on our contact page.

Valid til: May 27th, 2020

Code: MD10

Special: 20% OFF Black Friday Sale

We are running a Black Friday sale through the end of day on December 2nd at Tactical Transition! You’ll see some amazing deals posted throughout the site and none of which include the 20% off.. until you apply the code at checkout. Just enter BF20 on the checkout page and you’ll have the 20% discount applied. If you have any questions, feel free to shoot us a message on our contact page.

Valid till: December 2nd, 2019

Code: BF20

A Comparison of the AR-45 ACP vs AR 9mm

If you want to build a custom pistol caliber AR, there is one major decision to make first. Do you want to build it in 9mm or .45 ACP. There are differences and benefits to both. Lets Review them and go from there.

9mm, which is one of the most commonly used rounds today in the world, is always a favorite.The benefit of the 9mm is the controllability and the capacity, not to mention that these days it is fairly inexpensive to shoot.Some believe the 9mm is better for home defense because it will not penetrate as much as the .45 acp The 9mm also has less felt recoil than the .45 acp. 9mm has been used in our Military for over 30 years, and continues to be used today.

For the .45 ACP, the round has survived two World Wars, Korea, Vietnam, and has been used in our military up to the 1980s. Famous for major stopping power. It does have more penetrating power than the 9mm, and some believe bigger is better.

It is personal preference and either one makes a good choice for building an AR pistol or rifle.