Parts of the Firearm: The Barrel

In our previous post, we studied the bolt carrier group. In this post, we will study about the barrel of a firearm. We've actually talked a lot about barrels in a number of posts in the past, but never really discussed the parts of a barrel in detail. We will do that in this post.

A barrel is simply a tube through which a bullet comes out of. Most firearms these days have a single barrel, though shotguns do come in double barrel versions. This is in contrast to previous centuries when multi-barrel firearms did exist. In most cases, the barrels are cylindrical tubes, but there are also polygonal barrels and oval barrels which have been used in history. With that said, let us discuss the various terms that describe barrels.

Bore: This is a word that describes the inside of the barrel tube. The inside surface may be rifled (more modern) or smooth (i.e. smoothbore, which is what the first firearms were like).

Breech: This is the rear part of the barrel (i.e.) the end that is closest to the firing mechanism. Most modern firearms are loaded via the breech end of the barrel.

Chamber: The chamber is at the breech end of the barrel. This is the area where the cartridge is placed into, prior to firing it. The most pressure exerted on the firearm upon firing occurs in the chamber area, hence the walls must be thick enough to withstand this pressure. The manufacturing of the chamber has a lot to do with the precision and reliability of the firearm. If the chamber fits the cartridge very tightly and precisely, then accuracy of the firearm is improved, but the reliability of feeding a new cartridge into the chamber is reduced. Conversely, if the cartridge fits the chamber loosely, then the feeding of a new cartridge into the chamber is much easier, but when the cartridge is fired, it will move around in the chamber and affect the accuracy of the bullet. Therefore, a good chamber design tries to strike a balance between these two factors.

An exception to this are revolvers, which have multiple chambers in a separate cylinder. In this case, the chambers are not part of the barrel.

Freebore: In the case of rifled barrels, this is the area just forward of the chamber, but before the area where the rifling starts. It is a smooth area that guides the bullet forward where it engages the rifling.

Muzzle: This is the part of the barrel which the bullet comes out from. For early firearms, they were usually loaded via the muzzle end of the barrel. The pressure generated by the burning gases decreases as it approaches the muzzle. Hence, some manufacturers make the walls of the muzzle end of the barrel thinner than the breech end, since it doesn't have to withstand as much pressure and they can reduce the overall weight of the firearm this way.

Devices such as flash suppressors or compensators may be screwed on to the muzzle end of the barrel.

The length of a barrel depends on the type of firearm. Rifles and shotguns have barrels starting from around 17-18 inches in length and go all the way to 60 inches or longer. Revolvers and pistols tend to have barrels in the 3-5 inch range, though there are exceptions to this rule of course.

When a cartridge is fired, the expanding gases act on accelerating the bullet as long as it is still within the barrel. Once the bullet leaves the barrel, the expanding gases no longer act on it and the bullet is no longer accelerated. Hence, if the barrel is longer, then the expanding gases act on the bullet for a longer time and allow it to come out with greater velocity than if the barrel is shorter. On the other hand, longer barrels are harder to aim with. Hence, the design of a firearm must strike a compromise between these factors.

Cross-sections of three barrel types. Public domain image

In the above image, we see the cross-sections of three different barrel types. The left one is a smooth bore barrel, the middle one is a rifled barrel and the right one is a polygonal barrel.

Matchlock Technology: The Arquebus

The Arquebus was a type of firearm that was commonly used between the 14th and 17th century. It was a type of matchlock, the barrel was generally a smoothbore (i.e. it had no rifling) and it was loaded from the muzzle end (i.e. a muzzle-loader). The user was called an Arquebusier or a Harquebusier. The word is derived from Dutch Harkbuss which means a Hook-gun.

The Arquebus was first employed by the Chinese towards the middle of the 14th century and by early 1500, they had spread to Europe and were being used by Hungarian troops. Images of arquebusiers can be found in Rembrandt's famous painting titled The Night Watch.

Most early arquebusiers were usually knowledgeable about the construction of their weapon. Quite a few of them were the actual makers of their own weapons as well. The weapons weren't known for their accuracy, given the smoothbore barrel and primitive sights. A crossbowman or longbowman could fire with greater accuracy and range. However, firing a crossbow or longbow took literally years of practice to become proficient with the weapon, whereas an arquebus could be mastered by anyone in a lot less time. Once people had mastered the art of producing gunpowder and shot, it was easier to mass produce ammunition for an arquebus as well, whereas fletching (the art of making arrows) was still a craft that needed highly skilled labor to produce.

On the other hand, an arquebus was vulnerable to heavy fog and rain, since the user needed to keep his slow match lit. This is a problem with all matchlocks, as the article on matchlocks indicates. There was also a danger that the sparks from one person's arquebus could set fire to the powder supply of the person next to him. Unlike a longbowman, an arquebusier was generally helpless after his shot was fired and his weapon was heavier to carry, so it was not surprising that the bow was considered a superior weapon for many years.

To compensate for the arquebus's weaknesses, some strategies were evolved. For one, an arquebusier was sometimes accompanied by an assistant called a varlet, whose job was to help the arquebusier carry all his gear and keep a fire going. Since reloading took some time, tactics involved placing the arquebusiers in lines of three, so that when one line was done shooting, they could move to the back and reload, while the next two lines fired a volley each. Arquebusiers were also equipped with a sword as a second line of defence, if they couldn't reload in time. In order to compensate for inaccuracies of the weapon, commanders would line up several men next to each other and order them to shoot at the same time, in the hopes that at least some of them would hit the enemy troops.