In the picture on the left, notice that the cylinder is in its rearward position and that there is a gap or space that can be seen between the front of the cylinder and the rear of the barrel. Now take a look at the picture at the right. In the picture at the right, the hammer is back and the pistol is cocked. Notice now that the gap between the cylinder and barrel has disappeared and the cylinder is now in its forward position. This is normal and the pistol has actually been designed to operate in this fashion. This movement of the cylinder insures that the handgun has a hefty trigger pull and makes hitting the target while in double action mode difficult. I would not be surprised if most users of the Nagant pistol today fire it in single action mode when they are going for accuracy.
The Russian M1895 revolver design is really a classic example of over engineering that was applied to a problem that is largely imaginary. All revolvers will have a very slight gap between the front of the cylinder and the rear of the barrel. If this gap is not present, then the cylinder will not be able to turn, especially once it heats up and begins to expand from firing. Therefore a small amount of the high pressure and high temperature gases will escape from behind the bullet through this gap when the revolver is fired. Even the best built and most powerful revolvers of today have this gap and these escaping gases.
In the interests of accuracy, power and efficiency, the Russians were sold on the idea to eliminate these escaping gases. It has been proven that the loss of projectile velocity and ballistics from these escaping gases is negligible. The velocity of the bullet is increased by roughly 50 to 150 feet per second when the gases are not able to escape. This amounts to going to a lot of work for nothing in the way of manufacturing both firearms and the special cartridges that are required to complete the seal. What this pistol design did do was to allow for a silencer to be added to a revolver. Normally, the "bang" from the escaping gases in revolvers would make adding a silencer just about useless which is why handguns set up with a silencer are normally found as semi-automatic pistols that use sub-sonic ammunition.
When the hammer is pulled back either by the thumb or the squeeze of the trigger, the cylinder not only rotates but moves forward as well. There are recesses milled into the front of the cylinder that enclose the rear of the barrel. The 7.62mm Nagant projectile is deeply seated entirely within the brass cartridge case. The brass cartridge actually protrudes from the cylinder and closes part of the gap by fitting inside the conical section milled into the rear of the barrel. When the weapon is fired, the projectile expands the brass case as it moves through it and thereby completing the gas seal. To help illustrate the point, the picture below is of a loaded 7.62mm Nagant cartridge. It is actually quite impressive how the designers managed to accomplish all of this with such a modest number of moving parts in a revolver that is built as tough as a Russian tank.
How to unload the revolver after firing.
I know what you might be thinking, who doesn't know how to unload a simple revolver? Well, hang in here with me as there is actually a unique way to preform this function that is some what reminiscence of the old cap and ball handguns. After firing, the spent cases will have expanded inside the chambers and in most instances gravity will not be enough to clear them from the cylinder. The inset picture below shows a fully loaded 7.62mm Nagant cartridge. Notice that there is no projectile protruding out of the front. The front of this cartridge will expand as described in the text above when the weapon is fired and the empty cartridge will not clear the cylinder chamber unless the following procedure is preformed.
1. Swing open the loading gate on the right side of the receiver.
2. Unscrew the rod underneath the barrel and pull it forward.
3. Rotate the housing that is around the barrel toward the right.
4. Position the cylinder so that the rod can push out the spent case.
5. Rotate the cylinder and repeat.
As mentioned in the text at the top of this page, this is a laborious and time consuming process and not the most efficient design by any means for a military sidearm.
The Mosin Nagant rifle by Terence W. Lapin
Handbook of military rifle marks 1866-1950 by Richard Hoffman & Noel Schott
Official guide to gunmarks by Robert Balderson
The standard directory of proof marks by Gerhard Wirnsberger
Cartridges of the world by Frank C. Barnes