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-   -   The Gap Between The Cylinder And Barrel (http://www.firearmstalk.com/forums/f16/gap-between-cylinder-barrel-6458/)

Squirrel 08-21-2008 10:09 PM

The Gap Between The Cylinder And Barrel
 
I am not any kind authority on this, but from what I understand there is some kind of small gap between the cylinder of a revolver and the barrel; and that this gap is big enough that the the gas discharge from it is what prevented the revolver design from becoming popular for rifles. If this is so what keeps the bullet accurate as it crosses this gap so early on in its flight?

RL357Mag 08-21-2008 11:23 PM

Quote:

Originally Posted by Squirrel (Post 37303)
I am not any kind authority on this, but from what I understand there is some kind of small gap between the cylinder of a revolver and the barrel; and that this gap is big enough that the the gas discharge from it is what prevented the revolver design from becoming popular for rifles. If this is so what keeps the bullet accurate as it crosses this gap so early on in its flight?

Perfect alignment between the cylinder bore and the forcing cone. Over time this alignment is disrupted due to play in the lock-up of the cylinder. Several worn parts can contribute to this, and the most obvious indication of improper cylinder lock-up is lead splatter - this happens when the bullet is slightly off-axis with the barrel and is shaved on it's way into the barrel (forcing cone). In early brass framed revolvers, the frame would actually stretch, thereby creating problems with misalignment and excessive tolerances between the cylinder and forcing cone gap. This gap should ideally be only a few thousanths of an inch at most. I don't know if these problems are what prevented revolving carbines from becoming popular, so much as the design was actually dangerous. The support hand on early revolving carbines should not be placed forward of the cylinder to support the rifle, or gas burns would result - and in early black powder carbines, chain fires or multiple discharges would inflict serious injury. I had the unfortunate experience of a chain fire with a black powder revolver many years ago and had a .44 lead ball hit my supporting-hand thumb - it's NOT a pleasant experience!

genie 08-22-2008 12:40 AM

Look at the Gap
 
Squirrel, if you hold your revolver up sideways to a bright light, you can see the gap between the cylinder and barrel. It typically may be on the order of about 0.002" wide; that's the diameter of a human hair. The larger the gap (cheaper, poorly constructed revolvers) the larger the amount of high-pressure gas which escapes during firing. This escaping gas, especially in magnum calibers, constitutes a safety hazard to human parts, fingers, and such, held closer to the firing gun than a foot or so away. Occasionally, misalignment between the chamber and barrel causes fine slivers of metal to be shaved off and spat out sideways.

It is because of this gap that revolvers cannot be effectively "silenced", using a more-correctly referred to term, "suppressed".

Squirrel 08-22-2008 04:00 AM

Quote:

Originally Posted by RL357Mag (Post 37309)
This gap should ideally be only a few thousanths of an inch at most. I don't know if these problems are what prevented revolving carbines from becoming popular, so much as the design was actually dangerous. The support hand on early revolving carbines should not be placed forward of the cylinder to support the rifle, or gas burns would result - and in early black powder carbines, chain fires or multiple discharges would inflict serious injury. I had the unfortunate experience of a chain fire with a black powder revolver many years ago and had a .44 lead ball hit my supporting-hand thumb - it's NOT a pleasant experience!

When I was in the Atlanta History Museum, which predictably has a massive section on the Civil War, they had a whole section on early breech loading and repeating rifles, by the revolver rifles they said that the problem was that there would be a large gas discharge right next the operator's face; because the way a rifle is held, the cylinder is much closer to the face.

RL357Mag 08-22-2008 01:53 PM

Quote:

Originally Posted by Squirrel (Post 37350)
When I was in the Atlanta History Museum, which predictably has a massive section on the Civil War, they had a whole section on early breech loading and repeating rifles, by the revolver rifles they said that the problem was that there would be a large gas discharge right next the operator's face; because the way a rifle is held, the cylinder is much closer to the face.


That's possible also - but don't forget about the detacheable shoulder stocks made for colt revolvers. The concept was in use long before the revolving carbine came into being.

Bob Wright 08-22-2008 04:18 PM

The shoulder stocked revolvers were held differently than rifles. With a rifle, the off hand extends out to support the rifle at the fore end. With a stocked revolver, the supporting hand is held under the butt of the revovler. If not for the first shot, then for succeeding shots!

Barrel/cylinder gap has always been a bit of contention for many folks, but I just accept it as a fact of life. None of my animate targets ever knew the difference.

Bob Wright

RL357Mag 08-23-2008 12:35 AM

Quote:

Originally Posted by Bob Wright (Post 37419)
The shoulder stocked revolvers were held differently than rifles. With a rifle, the off hand extends out to support the rifle at the fore end. With a stocked revolver, the supporting hand is held under the butt of the revovler. If not for the first shot, then for succeeding shots!
Bob Wright

One should NEVER use the off hand to support the fore end on a revolver/carbine. The ever present danger of a chain fire dictates that the off hand always be kept behind the cylinder. I suspect many fingers and hands were blown off learning this lesson the hard way.

c3shooter 08-24-2008 01:42 AM

The cylinder gap generally runs .004 to .006 Less than that, the weapon is likely to bind when it gets hot, and parts expand. OLDER top break revolvers are even greater.

Want to improve accuracy? Pick a bullet long enuff that when the base is still in the charge hole of the cylinder, the front is entering the rifled portion of the barrel. 125 gr .357 are short, and not as accurate as 165 gr bullets. Yes, I know there are other factors that enter the equation. GOOD timing (the alignment of charge hole with barrel) is critical.

Bob Wright 08-25-2008 02:43 PM

I used to demonstrate the effect of blast at the barrel/cylinder gap to novice shooters:

Using a used target, tear a strip about two inches wide and 12~18" long, Using a full power .357 Magnum, or equal, drape this strip across the top strap of the revolver so it hangs down roughly centered on the gap. Then fire the gun. The results usually blow the paper to shreds, and make a lasting impression on the novice.

Bob Wright

Dillinger 08-25-2008 03:03 PM

Quote:

Originally Posted by Bob Wright (Post 37783)
I used to demonstrate the effect of blast at the barrel/cylinder gap to novice shooters:

Using a used target, tear a strip about two inches wide and 12~18" long, Using a full power .357 Magnum, or equal, drape this strip across the top strap of the revolver so it hangs down roughly centered on the gap. Then fire the gun. The results usually blow the paper to shreds, and make a lasting impression on the novice.

Bob Wright

Holy Crap! I think you and my dad used to get your firearms instructions from the same place. That is almost EXACTLY what he did to show me the seriousness of escaping gas from his revolver on the first time he took me shooting with it. He used an old tobacco pouch cut in half, but I still remember that "demonstration" today.... :D

JD


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