Actions: Break Open Action

When we last left off on our study of firearm mechanisms, we were still dealing with muzzle-loaders and the percussion cap. While we did study some details about breech-loaders, we really didn't study any of the mechanisms associated with them, aside from the Ferguson rifle. The rise of breechloaders started with the rise of metallic cartridges. In this post, we will study a common breech loader mechanism called the break-action. This is also called top-break or break-barrel action Actually, we did study a bit about break-actions in our discussion about revolver loading mechanisms earlier.

In a break action weapon, the barrels are hinged and break open on top to expose the chamber. One of the well-known examples is a Lefaucheux gun from 1836, which used pinfire cartridges.

There is a lump under the barrels through which a pin passes and the barrels pivot on this pin. There is also a slot cut into the other side of the lump. When the barrels are closed back in place, the user turns the lever in front of the trigger guard, which pushes a projection into the slot, thereby keeping the barrels from moving upwards.

When the barrels are tilted upwards, the user can remove the old cartridges, insert the new cartridges into the barrels and then close and lock the mechanism.

Of course, this mechanism was not always the strongest, but people began to improve upon this basic idea.

In the picture above, we have a W.W. Greener gun using his Treble Wedge-fast mechanism invented in 1865. This gun has three ways to hold the barrel in place. Under the barrels, notice the two projections with slots cut through them. A holding bolt through each one of these slots holds the barrels and prevents them from pivoting, when locked. In addition, notice the top of the barrel also has a projection with a hole through it. When the barrel is locked into place, a cross bolt is pushed through this hole to hold it in place. Each of these holding bolts by itself is capable of holding down the barrels, but the combination of all three together makes the action a strong one indeed.

In the picture above, we have a Greener Improved Treble Wedge-fast mechanism from the top view. When the user pushes the barrels back in place, they can use the long lever and lock all the bolts before firing the weapon.

Of course, it was soon realized that the movement of opening the barrels could also be used to cock the weapon at the same time and this was taken advantage of. Anson and Deeley made the first successful mechanism of this type in 1875, which was followed by other manufacturers such as Westley Richards, Greener, Purdey etc.

The mechanism above is an example of a Greener "Facile Princeps" mechanism. When the barrels are opened, the small lump C pushes one end of hammer A. Since the hammer turns about a pivot, opening the barrel turns the hammer A further back. As the hammer is pushed back, it also compresses the v-shaped spring B. The barrel is opened until the hammer cocks. This happens when A rotates sufficiently for the tip of lever D to hold A as shown in the image above. The weapon can now be loaded with cartridges and closed.

When the trigger is pulled, lever D is pivoted and thereby releases the hammer A. The spring pressure from the v-shaped spring B makes it open and thereby rotates A, which makes the beak of A sharply strike the center of the cartridge and fire it.

It was also realized that the action of the falling barrels could also be used to eject the old cartridges automatically as well. The first example employing this idea was the Needham gun of 1874, but variants of the basic principle were made by several others including Perkes, Anson and Deeley, Baker, Trulock, Ross, Holland & Holland etc.

In the above two images, the extractor lever is clearly visible. When the gun is closed, the extractor sits flush with the barrel. When the gun is opened, the extractor lever pokes out of the barrel and catches the rim of the cartridge and pushes it out of the barrel.

Thus, the user can eject the old cartridges and cock the gun at the same time, merely by the act of breaking open the weapon.

This action is a very compact and straightforward mechanism, which makes the cost of manufacturing pretty low. Since the extractor is part of the barrel, this makes it very suitable for guns that have interchangeable barrels.

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.