Difference Between Full Auto And Semi Auto Bolt Carrier: Which Is The Better Option?

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Full Auto Bolt Carrier Vs. Semi

Every adept gunner understands the importance of the gun bolt carrier. This component is like the heart of a rifle, which protects the bolt and facilitates the reloading process.

However, the beginners may get confused when they encounter the terms full auto bolt carrier and semi bolt. So, what are the functions of these two categories? Are there any differences in their performance?

This post will discuss the basics and functions of the full auto bolt carrier vs semi in detail. Based on the information provided, you can select a more suitable option for your needs and shooting style.

What is Full Auto Bolt Carrier?

A Full Auto Bolt Carrier refers to a specific type of bolt carrier group (BCG) used in firearms, particularly in rifles chambered for the 5.56x45mm NATO cartridge. It is designed to be used in firearms capable of fully automatic fire, such as select-fire or fully automatic rifles.

The bolt carrier group is a critical component of a firearm’s operating system. It consists of the bolt, bolt carrier, gas key, firing pin, and other related parts. When the firearm is fired, the bolt carrier group is responsible for cycling the action, extracting and ejecting spent casings, and chambering new rounds.

In the case of a Full Auto Bolt Carrier, it is specifically designed and manufactured to be compatible with fully automatic or select-fire firearms. It features certain design modifications to enhance the reliability and performance in rapid-fire or sustained automatic fire situations. These modifications may include differences in weight, dimensions, or geometry compared to semi-automatic bolt carrier groups.

It is important to note that in many jurisdictions, civilian ownership of fully automatic firearms or components, such as Full Auto Bolt Carriers, is heavily regulated or prohibited. It is essential to comply with local laws and regulations regarding the possession and use of such items.

What is Semi Auto Bolt Carrier?

A Semi Auto Bolt Carrier refers to a type of bolt carrier group (BCG) used in semi-automatic firearms, including rifles chambered for various calibers. It is specifically designed and manufactured for use in firearms that are semi-automatic only, meaning they fire one round with each pull of the trigger.

The bolt carrier group is a crucial component of a firearm’s operating system, responsible for cycling the action and facilitating the firing process. It consists of the bolt, bolt carrier, gas key, firing pin, and other related parts.

In the case of a Semi Auto Bolt Carrier, it is designed to function in semi-automatic firearms and typically lacks certain features found in Full Auto Bolt Carriers. The primary difference between a Semi Auto Bolt Carrier and a Full Auto Bolt Carrier is the presence of a sear trip or a mechanical feature that interacts with the firearm’s fire control group.

In semi-automatic firearms, the sear trip prevents the firearm from cycling in full-auto mode by not engaging with the auto sear. This prevents the firearm from firing multiple rounds with a single trigger pull, making it compliant with semi-automatic operation.

It is important to note that the specific design and features of a Semi Auto Bolt Carrier can vary depending on the firearm platform and manufacturer. It is always advisable to consult the manufacturer’s specifications and guidelines when it comes to selecting or replacing bolt carrier groups for a particular firearm.

Why Do You Need The Full Auto Bolt Carrier Or Semi?

When using the full auto or semi-auto bolt carrier, users regularly opt for firearms with closed bolts, such as the AR-15 rifle.

The closed bolts help increase shooting accuracy and smoothness while reducing the risk of bullet jam, thus giving you a more satisfying shooting experience.

However, closed bolt rifles like the AR-15 usually come with a locking mechanism. This mechanism increases the inner pressure inside the gun chamber as it seals the chamber and locks the breech.

As a result, it will burn more gunpowder, making the pellets leave the barrel with a higher speed and velocity. However, the round can only fire after the locking mechanism is fully activated, or it will damage the barrel.

The invention of the semi-auto is a solution to this problem. Unlike the fully sealed full auto bolt, the semi features a more open design with a chunk on the bottom or top of the bolt.

Due to this removed chunk, the semi is significantly lighter than its counterpart and facilitates the movement of the gun hammer. Therefore, the semi can fix the mentioned issue and reduce the risk of bullet jams when shooting.

The Full Bolt
The Full Bolt

The Differences Between Full Auto Bolt Carrier Vs Semi

To help save your time, I will go through the main strengths and setbacks of each category first. Then I will discuss the core differences between the full auto bolt carrier and semi in detail.

Short Summary

The semi-auto bolt carrier is technically easier to handle and use as the gun resets every time you hit the trigger. Meanwhile, some full auto bolt carrier variations are also capable of this feature.

However, you must equip them with some firearms that feature closed bolts. As mentioned above, the gun must reset after you fire the round, and fast shooting without fully resetting the bolt can cause a bullet jam.

The design of the semi-auto can fix this problem. As a result, it will bring a smoother shooting experience and a faster gun cycle. You can shoot at a higher speed smoothly with less risk of bullet jams.

Another noticeable advantage of the semi lies in its significantly lighter weight, which will make your rifle very light to hold. The semi is undoubtedly more comfortable if you have to hold and aim for an extended period.

On the other hand,  the full auto is heavier due to its fully sealed design. The open design of the semi also comes with a setback, which could wear down your gun carbine.

Meanwhile, the full auto bolt features higher durability and stiffness when shooting. The heavier weight makes your gun more stiff and firm to hold, resulting in a more robust shooting experience.

Lastly, you will experience less recoil when using the full auto bolt carrier. But its tradeoffs are the heavyweight and slower gun cycles.


When putting the full and semi-auto bolt carriers side by side, you can notice that the full bolt has a longer overall length.

Based on the specs measured on many product lines from different brands, the semi is generally lighter in weight.

Regarding the design, the full bolt carrier features a 2-inch rear section, making the gun cycle fully automatic. Meanwhile, the rear area on the semi-auto bolt has some parts and materials reduced with an open top or bottom.

In addition, the full bolt comes with a lug that you cannot find on the semi-auto bolt. Without this lug, you cannot utilize the full-auto function of the bolt.

It’s also this component that increases the overall weight of the full auto bolt.

The Semi Bolt Carrier
The Semi Bolt Carrier


The total weight of the bolt carrier varies on different product lines and brands, but the semi-auto products have a much lighter weight on average. It can be attributed to the design of the full-auto and semi bolts.

The full-auto has the additional lug and a sealed design, which significantly increases its total weight. Meanwhile, the semi bolt has an exposed area on the top or bottom which has been removed.

In addition, it doesn’t possess the lug, resulting in a significantly lighter weight than its counterpart. The difference can be felt just by holding the two gadgets using your two hands.

When holding a heavy firearm like the AR-15 rifle, a little weight reduction will bring more comfort to your shooting and aiming experience.

Recoil And Risks

Though the lighter weight of the semi-auto bolt carrier is an advantage, it will generate higher recoil. I have conducted shooting tests with rifles using both these categories.

While the semi-auto bolt generates pretty powerful recoil, the full-auto bolt gives a smoother shooting experience. This difference may be attributed to the heavyweight of the full-auto bolts.

Another issue you should consider is the higher risk of the “bolt bounce” on the semi-auto bolt. This issue is common in firearms that lack a locking mechanism.

When an automatic rifle is shooting, and the bolt isn’t fully charged, it may rupture the cartridge and lead to an explosion inside the barrel. With the lug on the bottom, the full-auto bolt can reduce this potential issue more effectively.

Furthermore, the heavyweight of the full-auto bolt carriers also increases their durability. It can reduce the stress generated on the barrel when shooting, thus reducing the risk of wearing down or internal damage.

The Classic AR-15 Rifle Uses The Semi Bolt
The Classic AR-15 Rifle Uses The Semi Bolt


Nowadays, the full-auto bolts are still more popular since it was invented much longer than the semi. Meanwhile, the semi-auto bolt carriers are pretty rare and only available on some specific rifles with closed bolts.

You can definitely find both categories in any gun store or market, but the full-auto bolt will give you more options and higher availability.

If you need further reviews and in-depth comparisons between the full-auto bolt carrier vs semi-auto, consider watching the video below.

Final Verdict

So, which is the better option between full-auto bolt carrier vs semi-auto bolts overall?

To sum up, the main difference between these two categories lies in their designs. The full-auto bolts come with a mass in the back, while the semi-auto bolts have a cut-out part on the top or bottom.

There’s a common misconception that the full-auto bolts will make the firearms fully automatic, but it’s not true. However, the higher mass and greater durability of the full-auto bolts are surely a plus point.

If you prefer a more robust shooting experience with higher recoil and faster gun cycles, the semi-auto bolts are more suitable. Meanwhile, the traditional full-auto bolts are more popular and bring higher durability.

I hope that the information provided can help you choose the most suitable category for your needs. Thank you for your time!

Last Updated on October 28, 2023 by

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