Tuesday, December 10, 2013

What is a "Cylinder Gap"?

In today's post, we will look into the topic of revolvers and firearms safety and also study the concept of cylinder gaps.

If the reader looks at a revolver, chances are that the reader may observed that, at the area where one of cylinder's chambers aligns with the barrel, there is a small gap between the front of the chamber and the barrel, about the thickness of a business card. This space is called the cylinder gap.

This gap exists in all revolvers, because there needs to be a bit of space between the cylinder and the barrel, in order to allow the cylinder to rotate. In some revolver designs (e.g. the Belgian Nagant 1895 model), this gap is sealed when the weapon is cocked (we will look at this design in a future discussion), but in most revolver designs, this gap is left open at all times.

When a revolver is fired, high pressure gases are generated in the chamber and expand into the barrel, pushing the bullet out. While most of these gases expand into the barrel, a small amount of hot gas comes out of the sides of the cylinder, due to the cylinder gap. If the chamber does not precisely align with the barrel, some metal particles may come out of the side as well. These hot gases and particles come out with a surprising amount of energy, even on a small revolver, and may cause some serious injury. Therefore, it is unwise to place a hand ahead of the cylinder, or even stand close to the side of the person firing the revolver.

Correct ways to hold a revolver

In the above images, we see the correct ways to hold a revolver. Notice that in both cases, the person ensures that the hands are placed well behind the cylinder gap. Now we will look at the incorrect way to hold a revolver.

Incorrect way to hold a revolver. Never do this!

In the above image, we see an incorrect way to hold the revolver. Notice that the user has some fingers placed in front of the cylinder. This is a very bad idea and could result in serious injury, if the revolver is fired. People who are new to revolvers may accidentally do this, because they find it easier to support a heavy revolver, or because they see people doing it with pistols, and they cause injury to themselves.

The above video demonstrates pretty well, how much gas can come out of the sides of the cylinder and why it is a bad idea to put any body parts close to the cylinder gap. In fact, people standing close to the sides of the revolver may feel the hot gases as well, which is why it is best to stand behind the shooter, or some distance away to the side.

The reader may wonder, why is it that gases don't come out of the back of the cylinder? Well, that is because when the revolver is fired, the heat of the explosion causes the sides and back of the cartridge to expand slightly and the rim seals off the back of the cylinder and prevents most of the gas from leaking out of the back.

Due to the leakage of gases through the cylinder gap, the velocity of the bullet coming out of the revolver is slightly reduced. There are designs that attempt to close this gap when firing, so that the entire energy of the expanding gases acts upon the bullet. We will study these designs in a future post.

1 comment:

  1. What is the gap for a Uberti 1875 Outlaw Colt 45 Long Colt?