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.
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.
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.