How do Firing Mechanisms Work - III

In our last couple of posts, we saw a couple of examples of semi-automatic, full automatic and three round burst mechanisms. The first video was prepared by the US Army to train soldiers. As it turns out, the Army had actually prepared a set of videos. The first in the series showed an example of a bolt-action firearm in action. We will study that video in today's post:

Interestingly, the video shows a hammer fired and a striker fired mechanism and also deals with extraction and ejection mechanisms, as well as loading new ammunition from a box magazine.

Happy viewing.

Revolver: Loading Mechanisms

We have devoted the last few posts to studying revolver firing mechanisms. Now we will spend some time in studying revolver loading mechanisms.

The early revolvers such as the first Colt Paterson models of 1836 had a very primitive reloading mechanism. As these revolvers were muzzle-loaders using percussion-cap technology, the user was required to disassemble the gun to reload it. The user would first put the hammer at half-cock, then open a latch in front and pull out the barrel and cylinder from the revolver frame. The user would then fill the cylinder's chambers with gunpowder and a ball in each chamber. Then the user would tamp each ball down with a ramrod. Then the user would assemble the gun back and then attach percussion caps to the back of each chamber. The small revolver on the picture above is a Colt 1836 model.

Obviously, such an operation took a long time. Hence, some people would walk around with already loaded spare cylinders in their pockets. That way, all they had to do was to pull out the barrel and cylinder from the revolver frame, substitute the new pre-loaded cylinder and reassemble the gun.

The Colt Paterson model of 1839 improved on this by putting a loading window on the side of the weapon, near the front of the cylinder. Colt also attached a ramrod on a hinge, on the underside of the barrel. Using this system, the user did not need to disassemble the revolver to reload any longer. Instead the user would put the gunpowder and ball into the chamber that is next to the loading window. Then the user would unhinge the ramrod and use the lever to ram the ball into the chamber. The user would repeat this operation until all the chambers were reloaded. The two crossed revolvers in the picture above are Colt 1839 revolvers.

With the advent of metallic cartridges, the next mechanism that was used was the fixed cylinder/loading gate concept.

In here, there is a hinged loading gate near the back of the cylinder. The gate cover can be slid open and then, metallic cartridges can be removed or loaded one at a time into the loading gate. The cylinder can be rotated after each chamber is loaded, to bring the next chamber in line for reloading. The gate cover is closed after the desired chambers are reloaded. The Colt Peacemaker was one of the weapons that used this reloading mechanism. Since the cylinder is attached to the solid frame of the weapon in both the front and the back, revolvers using this loading mechanism are generally very strong weapons. This is why large caliber revolvers that fire powerful cartridges tend to use this reloading mechanism. The disadvantage of this mechanism is that each chamber needs to be loaded/unloaded one at a time.

The next reloading mechanism we will study is the top-break mechanism. In this mechanism, the revolver is hinged near the front-bottom of the cylinder.

The user can open the revolver as shown in the picture above and load new cartridges in quickly and easily. In fact, many users use a speedloader, which is a simple device that holds the cartridges in a circle corresponding to the chambers of the revolver. A picture of a typical revolver speedloader is shown below.

The user simply puts the speedloader on top of the cylinder and unlocks the speedloader, which drops all the cartridges simultaneously into all the chambers of the cylinder.

In many top-break revolvers, the action of breaking open also pushes an extractor lever upwards, which ejects out all the old cartridges, or moves them far enough out of the cylinder that they can be pulled out easily.

In the picture above, you can see the old cartridges being expelled by the extractor of a Smith and Wesson revolver as it is being opened. In many models, the auto-extractor is powerful enough to eject the fired cartridges, but is not strong enough to completely eject the longer, unfired cartridges. These are merely lifted away from the chambers by the extractor and not ejected out of the weapon completely.

The advantage of the top-break design is that it allows faster reloading as all the chambers can be loaded simultaneously. If the weapon has an auto-extractor, then the reloading becomes even more faster, as the user doesn't need to manually extract the old cartridges. The disadvantage is that the design isn't as strong as the fixed cylinder design and cannot be used for high-powered cartridges.

The next mechanism is the swing-out cylinder mechanism. In this, the cylinder is mounted on a pivot that swings out and down.

Public domain image from wikipedia.com. Click to enlarge.

As can be seen in the picture above, the rod in front of the cylinder unlocks the mechanism and allows it to swing out. The rod can then be pushed in to operate the extractor and eject out the fired cartridges. As with the top-break design, the extractor is designed so that unfired cartridges are not completely ejected from the chambers. Loading can then be done one at a time, or simultaneously using a speedloader. After loading, the cylinder is pushed back to the body of the revolver and then locked in place.

In the above diagram, you can see the close-up of the star-shaped extractor plate. When the revolver is closed, it sits flush with the cylinder. When the extractor plate is pushed away from the cylinder, it catches the rim of all the cartridges loaded in the cylinder and pushes them out of their chambers.

This is a modern design and is much more sturdy than the top-break mechanism. However, it is not as strong as the fixed-cylinder design. On the other hand, it is much faster to reload than a fixed-cylinder model.

Loading Mechanisms: Breechloader

In the previous post of this series, we've discussed the development of the muzzleloader . Now we will consider the other loading mechanism: the breechloader. To recap, a muzzleloader is loaded via the open end of the barrel (or muzzle). A breechloader is loaded near the closed end of the barrel (i.e.) near the trigger. The barrel is usually opened via a hinge or a plug, the gunpowder and bullet are put in and then the hinge is closed. One of the main advantages of breechloading weapons over muzzleloaders is that they are much quicker to reload. Another advantage is that the shooter doesn't need to expose himself to enemy fire to reload the weapon. With a muzzle loader, one must stand the weapon up vertically, put the safety on, stand up and pour the powder down the barrel and then use the ramrod to shove the bullet home into the base of the barrel. With a breechloader, one simply breaks open the breech, loads in the cartridge and then closes the breech and fires. The figure below shows a 16th century breechloading weapon that opens via a hinge.

Public domain image courtesy of wikipedia.com

The breechloader mechanism was known in the early history of firearms, but didn't really become popular until around the mid 19th century, because breech loading weapons need more precision manufacturing than muzzleloaders to actually work. After the 19th century, when manufacturing techniques reached the required standards, virtually all modern weapons made since then are breechloading.

The main challenge of breechloading weapons is to find a good way to seal the breech so that the expanding gases don't escape out that way. One of the early ways was by using a screw plug, as in the case of the Ferguson rifle, which will be studied below. The later development of metallic cartridges contributed much more to modern breechloader development.

The Ferguson rifle was invented by one Major Patrick Ferguson of the British Army in 1776.

Public domain image courtesy of wikipedia.com

It consisted of a screw plug at the breech, which could be unscrewed by turning the trigger guard. The user would tilt it forward and initially load in a lead ball of a slightly larger diameter than the barrel. The lead ball would roll forward and get stopped by the start of the barrel threads. Unlike most muzzleloaders, the ball did not need to be wrapped in a cloth or paper patch to provide a tight seal, since it was a slightly larger diameter than the barrel. Then the user would pour in some gunpowder to fill the loading chamber and then turn the trigger guard the other way to screw the plug back in. Excess gunpowder in the breech would be sheared off by the screw plug rising back up. Then the user could cock the weapon and be ready to fire. The firing mechanism itself was a flintlock, which was the height of firing mechanism technology at that time. Upon firing, the lead ball would slightly deform and keep the tight seal as it made its way through the barrel.

Such a loading mechanism was already known in Ferguson's time. In fact, one John Warsop had invented a similar mechanism and received a patent back in 1720. However, Warsop's design had a single threaded screw and needed 4 to 12 complete turns to open the breech for reloading. It was also loaded from the bottom and therefore more cumbersome to load. The innovative features of Ferguson's design were:

1. Use of a twelve start thread screw plug instead of a single start thread like the Warsop design (i.e.) the screw had 12 separate threads spiralling from the top to the bottom. Hence, instead of turning the screw plug 12 times to unscrew it like the Warsop design, it was only necessary to turn the screw plug once in a Ferguson rifle to unscrew the plug.
2. Top loading mechanism, so the user could drop the ball and gunpowder from the top.
   
3. The screw threads were interrupted by vertical slots cut into them Some excess powder would fall into these gap between the screw threads when the plug was screwed back in, and the remaining excess fouling could simply be wiped off.
4. The top of the screw plug was of a slightly larger diameter than the screw hole. What this meant was that the screw plug could not be removed from the rifle even if it was fully unscrewed. This was done so that it is not possible to drop the screw plug even in the heat of combat.

A good rifleman using a Ferguson rifle could load and shoot up to 6 rounds per minute. Major Ferguson himself demonstrated the rifle to senior officers on a very rainy summer day of 1776 and got their approval. To quote a newspaper of that time,

"Length 50 in.; weight 71/2 lbs.; bayonet 25 in. long and 11/2 in. wide, and being of fine temper and razor edge was called a sword bayonet; folding rear sight with leaves of 100 to 500 yds. The rotating breechblock has 12 threads to the inch, and opens or closes with one complete whirl of the guard. When open, the top of the screw is level with the breech bottom, a ball dropped in slides forward into a chamber slightly larger than the rifled diameter, the muzzle is tipped downward, powder put in to fill the chamber back of the ball, the guard is turned and the screw rises to the top and removes any surplus powder, while making the breech gas tight. When fired, the ball takes the rifling."

Unfortunately, there is a big difference between getting approval and gaining widespread acceptance and orders were initially placed for 300 weapons, of which only 200 were made and these were delivered to Ferguson's own unit (and were withdrawn from service shortly after, in spite of their success in the Battle of Brandywine).

There were a couple of reasons for the failure of this innovative weapon. The first was that the senior military officials didn't think it was manly at that time for soldiers to reload and fire while lying under cover in a prone position. Standard tactics of that era called for soldiers of opposing sides to meet face to face and shoot each other standing up.

The second reason for failure was the cost of manufacturing. It cost approximately 4 pounds to manufacture a Ferguson rifle, whereas a muzzle loading "Brown Bess" musket cost only 2 pounds at that time. It also took a skilled gunmaker more time to make a Ferguson rifle than a Brown Bess. Manufacturing a twelve-start thread screw plug required very specialized skills and not all gunmakers at that time could make those. At a time when the British Army would need to manufacture 50,000 rifles to replace their existing Brown Bess muskets, the total capacity of skilled gunmakers in England who could make the twelve-start thread screw plug was approximately 1000 per year. While mass production technologies for manufacturing were being pioneered during the time that the Ferguson rifle was being developed, no one in England thought to apply them to gun manufacture. It was left to the Americans, specifically Eli Whitney, to do this in 1790.

So despite the success of the weapon in the Battle of Brandywine, Ferguson's superior ordered the rifles to be locked up in a New York warehouse and his own unit was re-equipped with Brown Bess muskets. The remaining orders were also cancelled and thus the Ferguson faded into obscurity. It was not until a century later that breechloaders became popular again.

Loading Mechanisms: Muzzleloader

Now we will move on to loading mechanisms. The first loading mechanism we will consider is the muzzleloader (i.e.) a weapon that is loaded from the muzzle end (the open end) of the weapon. Since muzzleloaders were easier to manufacture, early firearms were virtually all muzzleloaders. The diagram below shows a typical flintlock muzzleloader weapon.
To load the weapon:

1. The user first enables the weapon's safety mechanism so that it cannot go off when loading. In the case of a flintlock, the user puts the mechanism at half cock and pushes the safety lever. In the case of a matchlock, the user makes sure the lit match is kept well away from gunpowder.
   
2. The user places the butt of the gun on the ground, taking care that the barrel is pointed away from the user.
3. The user takes their powder from their powder horn (a conical container hanging from the waist that contains gunpowder) and pours out a certain amount of gunpowder into a measuring tube or measuring flask.
4. The user then closes the powder horn and returns to their waist. The user then pours the powder from the measuring tube into the top of the muzzle (or barrel). The user also taps the barrel a bit to make sure the powder has settled in the bottom of the barrel near the pan.
   
5. The user then takes a bullet (in those days, it was a ball) and wraps it in a patch of lubricated paper or cloth to surround the bullet. Since the diameter of the bullet is usually smaller than the barrel, the patch surrounding it ensures a tighter fit.
   
6. The user then pulls out the ramrod which is a long thin rod stored under the barrel and uses it to push the bullet all the way into the barrel, so it is sitting on top of the gunpowder. The user then returns the ramrod to its storage tube under the muzzle.
7. The user now lifts the weapon off the ground and opens the cover over the pan (called the frizzen for flintlocks and pan cover for matchlocks and wheel-locks). The user then adds some priming gunpowder into the pan and closes it. In the early days of firearms, the priming gunpowder was finer than the main gunpowder in the barrel.
   
8. The user then cocks the rifle to full cock and disables the safety mechanism. Now the weapon is ready to fire.
   

This procedure is a bit cumbersome and many developments were done to speed this up. For instance, in the above diagram, you may note that the gun has a compartment (patch box) in the side to store patches of lubricated paper or cloth, so that's one less thing that the user has to fumble around to find.

In later flintlocks, the gunpowder was developed so that there was no need to carry around any separate priming gunpowder. The user would simply pour gunpowder down the barrel and a little would dribble out of the bottom of the barrel through the touch hole into the pan and the user would top it off with a little more from their powder horn. The same gunpowder was fine enough to be used as both a priming powder, as well as the main powder charge.

Then came the invention of the paper cartridge. Instead of the user carrying around a powder horn, a bag of bullets, another bag of patches, a separate horn of priming powder and a measuring flask or two, the user would simply carry paper cartridges, each containing a bullet and a pre-measured quantity of gunpowder. The outer paper casing of the cartridge would be lubricated with grease, lard or beeswax so that it could be used as a patch. The greasy outer casing also had a couple more advantages: it made the cartridge somewhat water-resistant and on firing, the grease or wax would melt and mix with the gunpowder residue, making it easier to clean the barrel. All the user had to do was tear off the top of the paper packet with their teeth, pour the gunpowder in the cartridge into the muzzle, then use the paper to wrap the bullet and push it down the tube with the ramrod. A little bit of the left over powder could be used to fill the pan if needed.

These advances made loading muzzleloaders much faster. The new cartridges were also one of the causes of the Great Indian Mutiny. A rumor that spread among the Sepoys (i.e. Native Indian soldiers) was that the cartridges were greased with the fat of cows and pigs (which were animals revered by the Hindus and treated as offensive by the Muslims) and by tearing the cartridges with their teeth, they would defile themselves.

Muzzle loading weapons stayed popular for quite a while. Famous weapons such as the Brown Bess musket served the British infantry for over 100 years.