Smoothbores and Rifled Bores

It was mentioned in the post on artillery production about how some cannon were bored and reamed to size while others had the added step of rifling during production.  It sounds simple enough, but there may be readers who do not understand just what this means.  As it is pertinent to understanding the next few posts on artillery, we shall address this topic now.

First off, the main hole in an artillery piece or any firearm for that matter is known as the bore. The bore is contained within a long metal tube known as the barrel.

6 Pounder barrel

 The term "Smoothbore" comes from the simple fact that the bore is just that, smooth.  The projectile is not controlled in any meaningful way as it exits the muzzle. What is the projectile fired from these cannon?  That question will have to wait until the posts on artillery ammunition.

6 Pounder bore

The purpose of rifling was to impart a spin on the projectile to increase the accuracy and range of the round. It is a cliché example to be sure, but watch a slow motion replay of a Quarterback in American football throwing a pass. You can see the ball spinning as it flies through the air.  The combination of shape and how the ball is thrown increases the accuracy of the throw and allows a skilled Quarterback (or gunner) to put that pass exactly where it is intended.



Rifling inside Hughes gun, Confederate Breechloader

Rifling consists of spiral grooves cut down the length of the bore.  The projectile follows these grooves and thus gains the intended spin. These grooves can be seen in the example photograph above. The "light at the end of the tunnel" wasn't a round at the exact instant of firing! It was simply a piece of paper placed there to reflect light and permit easier viewing of the public down the bore. If you compare the two bore on photographs the lack of rifling can clearly be seen in the six pounder compared to the Hughes gun.


Next time in artillery we will begin to discuss the guns themselves, beginning with the smoothbore pictured above, the six pounder.

-Corporal