Large Fierce Mammal

No. It’s not.

Figure 1: A Maschinengewehr 08 (MG08) air cooled light machine gun of the World War 1 (1914-1918) era. This weapon was based on the “Maxim Gun”, designed by Hiram Maxim in 1884. Note the ventilated barrel shroud that protects its operators from the inevitable heat generated by firing. (click the image to enlarge)

This is the second in my Short, Easily Digested Firearms Education Lecture series – the first being my article on the clip and the magazine.

If you’ve read the first two installments in my What in the Name of Hell IS an Assault Rifle Anyway? series (part 1 here, and part 2 here), you will know that what is being widely touted today as new news in firearms development is anything but. And so it is with the topic of today’s discussion – the “barrel shroud”.

It’s interesting that people involved in writing legislation aimed at regulating civilian access to certain types of firearms have included the barrel shroud as one of the attributes that defines the line between freely available and absolutely not. The concept has been around for a long time, and far from contributing to the power or lethality of the weapons to which it has been attached, a barrel shroud is nothing more than an extension of a firearm’s receiver (the receiver is the framework all the other parts attach to) that extends over and surrounds all or part of the barrel. In many applications it’s no more than a heat shield, and depending on the firearm, may also double as the fore-end of the stock (this being the portion of a gun stock that lies under the barrel, but ahead of the trigger, and in long guns is supported by the hand that is not engaged in firing). Keep that in mind as we go forward here – a barrel shroud is either a protective cover, a forward hand hold to support the barrel during firing, or both. In modern firearms it may also serve as a platform for mounting accessories like lights and special sights, but in itself it does nothing to change the way a firearm operates or increase its lethality.

Barrel shrouds originated about the same time as rapid firing firearms, most particularly the machine guns that made their appearance en masse in the battlefields of the War to End All Wars, otherwise known as World War 1  (1914-1918). A weapon that fires repeatedly, and in rapid succession, gets hot, and fast. In the excitement and confusion of combat, it’s easy for human flesh to come into contact with hot gun barrels, with predictably ouchy results. It should be pointed out that this heating effect isn’t limited to self-loading (semi-automatic or fully automatic) firearms. On the range I’ve received and observed burns occurring in bolt, lever, and pump action firearms, and expect that I will again.

Figure 2: The Fokker Dr.I Dreidecker (triplane) was armed with a pair of MG08 machine guns. (click the image to enlarge)

An early representative example of a barrel shroud can be seen in air cooled versions of the Maschinengewehr 08, or MG08 (Figure 1), which was the standard machine gun of the German army through World War 1, and until it was finally withdrawn from front line service in 1942. This weapon saw extensive use both on the ground and in the air, and was used to good effect by such notables as Manfred von Richthofen who had two of them bolted to the front end of his famous Fokker Dr.I Dreidecker (triplane) (Figure 2).

Figure 3: The STEN submachine gun. (click the image to enlarge)

Moving forward in history to lessons learned in World War 2, we see the barrel shroud appearing in weapons not only as a heat shield and a fore-end to be gripped by the non-firing hand, but also as a means of building weapons as cheaply as possible. Witness the “plumber’s nightmare” – the STEN submachine gun (Figure 3)- that was a staple of Commonwealth armies and those supplied by them throughout WW2 and for many years thereafter. Polish by marriage as I am, I find a small amount of happiness in the fact that the STEN is called pistolet maszynowy STEN in that fair land.

The STEN was the British answer to a small arms concept that had been widely embraced by Germany – a compact, light weight, cheap to build, fully automatic weapon that fired pistol ammunition, and that could be issued to troops that either didn’t need a full sized rifle, or that because of their mission would not be well served by one, yet still needed more fire power than a pistol could afford. The answer – a weapon that consisted of a short rifled barrel, a spring driven reciprocating bolt equipped to feed, fire, extract, and eject cartridges, a side mounted quickly changeable magazine, all held together by welded steel tubes and plates. Equipped with a picture and a description of how it works, any machine shop could turn one out in a few hours.

Figure 4: The Sterling submachine gun, widely issued by Commonwealth armies, including Canada where it was referred to as the SMG C1. (click the image to enlarge)

Post war evolution of the STEN led to the Sterling submachine gun that was widely issued by Commonwealth armies, including Canada where it was referred to as the SMG C1 and issued until 1988. Note from Figure 4 at right that the main body of this weapon is one continuous tube forming the receiver and the hand guard (barrel shroud), making it very efficient – and by that I mean cheap – to manufacture. A common thread in pretty much everything made in the modern era.

Figure 5: The C8 carbine. (click the image to enlarge)

Coming forward to the present day in which all armies are equipped with true assault rifles, I’ll illustrate the progress of the barrel shroud concept with a rifle that is not available to the civilian market, but that is routinely fielded by Canadian military and police forces – the C8 carbine manufactured by Colt Canada. The C8 – a direct descendant of the original Armalite AR15 that evolved into the M16, and a military version of the strictly semi-automatic civilian AR15 of today – is a true assault rifle in that it chambers an intermediate power rifle cartridge and is selective fire; i. e., capable of semi-automatc or fully automatic fire as the situation requires. What you see in Figure 5 is the manufacturer’s representation of the basic C8 with a simple fore-end made of plastic. In this, the fore-end is a true barrel shroud in that it surrounds the barrel but doesn’t actually touch it. Let’s look at why this is done.

Back in the days when all rifles were old school and hafted in good old hard wood, the people who built them were craftsmen, and the ones who fitted all that beautifully blued steel into walnut were masters of an art called “bedding”. I hate to keep bringing it up – no, wait, I don’t actually – but the principles underlying bedding are to be found in … say it with me … Physics.

A rifle is first and foremost a precision tool designed to deliver a projectile to targets within its design range with a high degree of repeatable accuracy. A rifle barrel may be made of steel, and it may appear to be rigid, but in fact when it’s held horizontally and not otherwise supported, it droops under the effect of gravity. Not a lot, and your eye will never be able to see it, but it does. Firing a bullet down it will cause it first to straighten, and then to whip the muzzle above the barrel’s center line in a sinusoidal process called “barrel whip”. This can be seen in action in the following video in which a 5.56 x 45mm Ruger Mini-14 (firing the same cartridge as the AR15) is fired in front of a slow motion camera.

Accuracy requires that each bullet fired exit the barrel at exactly the same point in the barrel whip process, also referred to as barrel harmonics. Anything that interferes with the harmonics of a barrel will change the point of impact for bullets fired. This is why hunters don’t rest the barrel of their rifle on a support before taking a shot, instead resting the fore-end of the stock which is designed to support the barrel. Otherwise, the barrel will appear to leap upward from the support causing the muzzle to be elevated above the intended sight line as the bullet leaves the muzzle, causing the shot to go high and wild.

In a traditional bedded rifle stock, the barrel rests in a channel that is cut into the wood (or often these days, machined or molded into plastic) to receive it. The stock touches the barrel only at specific points, and then only with a pressure that falls within very specific limits – the fore-end of the Lee Enfield rifle stock, for example, must apply a specific amount of upward pressure on the muzzle end of the barrel to achieve maximum accuracy. Alternatively, there is the concept of the “free floating” barrel in which the barrel is supported at its breech (rearward) end where it attaches to the rifle, but touches nothing else but air along its length. A lot of the artistry in rifle bedding comes from knowing your materials because rifle stocks made of wood change dimensions slightly depending on ambient temperature and humidity – clearly undesirable traits that will alter point of impact if not taken into account – but free floating barrels are immune to this. In their case, barrel harmonics are unimpeded by environmental factors, and this is the method often used in the latest generation of rifles, because it permits construction of accurate firearms by means that rely heavily on automation. Rifles like the Colt Canada C8, and those of the semi-automatic AR15 variety for example, rely heavily on alloy casting and computer controlled machining to build what once would have required the attention of a team of craftsmen with decades of experience.

To recap then, a barrel shroud is an extension of a firearm’s receiver (the receiver is the framework that all other parts attach to) that extends over and surrounds all or part of the barrel. That is it. Most importantly of all, it is not, “… the shoulder thing that goes up.”

No. It’s not.