Revolver friends: what is the function of the forcing cone?

Revolver friends: what is the function of the forcing cone?

This is a discussion on Revolver friends: what is the function of the forcing cone? within the General Firearm Discussion forums, part of the Related Topics category; - what does the forcing cone do? - does it re-direct some gasses back to the cylinder to ensure the cylinder and barrel are aligned? ...

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Thread: Revolver friends: what is the function of the forcing cone?

  1. #1
    Member Array starlights's Avatar
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    Revolver friends: what is the function of the forcing cone?

    - what does the forcing cone do?
    - does it re-direct some gasses back to the cylinder to ensure the cylinder and barrel are aligned?
    - help me understand.
    - thank you.











    ?
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  2. #2
    Member Array M1911A1's Avatar
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    The forcing cone is a feature of a revolver's barrel, to be found at the end which contacts the cylinder's chamber mouths.
    It is, essentially, a short funnel shape, cut into the barrel's interior.
    Its function is to compensate for minute misalignments of chamber-bore and barrel-bore.
    As the bullet is propelled from the chamber in the cylinder, across the slight gap, and into the barrel, that bullet first encounters the forcing cone before it enters the barrel's rifling. Thus, the bullet has the space to straighten its flight, guided by the forcing cone's funnel shape, before entering the rifling.

    Does that help?
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    Member Array starlights's Avatar
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    Quote Originally Posted by M1911A1 View Post
    The forcing cone is a feature of a revolver's barrel, to be found at the end which contacts the cylinder's chamber mouths.
    It is, essentially, a short funnel shape, cut into the barrel's interior.
    Its function is to compensate for minute misalignments of chamber-bore and barrel-bore.
    As the bullet is propelled from the chamber in the cylinder, across the slight gap, and into the barrel, that bullet first encounters the forcing cone before it enters the barrel's rifling. Thus, the bullet has the space to straighten its flight, guided by the forcing cone's funnel shape, before entering the rifling.

    Does that help?

    - yes thank you
    - how is the cone able to take that continual abuse?
    - is it a matter of the bullet being softer and the cone being harder?





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    VIP Member Array forester58's Avatar
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    Quote Originally Posted by starlights View Post
    - yes thank you
    - how is the cone able to take that continual abuse?
    - is it a matter of the bullet being softer and the cone being harder?





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    If the revolver has proper timing it really doesn't take heavy abuse because it lines up correctly when it locks up. That said one of the main things to look at when buying a used revolver is the condition of that forcing cone, the reputable sellers on places like Gunbroker always include a close up picture of the forcing cone for this reason. If you look at used revolvers long enough you will see forcing cones that have rough blasted edges. A good used revolver buying thread is pinned on this site.
    A revolver with bad timing will shave lead or copper and spit it sideways which is another reason not to stand off the the side of a revolver when someone is shooting one. Even well built guns fed a steady diet of hot magnum loads like the hotter 125 grain 357 magnum will accelerate wear on the forcing cone but, we are talking 10's of thousands of rounds. Most guns today will last several lifetimes of steady shooting and by the time the forcing cone wears out your frame is probably stretched beyond spec anyway causing excessive end shake.
    One of the reasons revolvers are so expensive compared to semi autos is they require final hand fitting for correct timing. Revolvers are tough guns but, they have their weaknesses like dropping with an open cylinder or people that flip the cylinder closed like some Hollywood dip. Both of those can damage the timing on a revolver by even very minor bending of the crane or locking problems by bending the extractor rod.

  6. #5
    Distinguished Member Array TSKnight's Avatar
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    Picture of the forcing cone on my S&W 27-2. Sorry the picture quality isn't great.
    If you look close you can see a little cutting at the bottom of the bore where the rifling starts.

    Revolver friends:  what is the function of the forcing cone?-img_20191109_093538.jpg
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    VIP Member Array OldVet's Avatar
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    Consider it the feed ramp for revolvers.
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    VIP Member Array WC145's Avatar
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    Quote Originally Posted by M1911A1 View Post
    The forcing cone is a feature of a revolver's barrel, to be found at the end which contacts the cylinder's chamber mouths.
    It is, essentially, a short funnel shape, cut into the barrel's interior.
    Its function is to compensate for minute misalignments of chamber-bore and barrel-bore.
    As the bullet is propelled from the chamber in the cylinder, across the slight gap, and into the barrel, that bullet first encounters the forcing cone before it enters the barrel's rifling. Thus, the bullet has the space to straighten its flight, guided by the forcing cone's funnel shape, before entering the rifling.

    Does that help?
    The only thing I'll add is that the barrel/forcing cone should not come in contact with the cylinder. There is a small gap there to allow the cylinder to move freely.

    The only exception to that that I can think of is the old Nambu revolver, IIRC, the action pushed the cylinder forward against the barrel when the trigger was pulled, eliminating the barrel/cylinder gap during firing.
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    VIP Member Array LimaCharlie's Avatar
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    You never want your fingers or other body parts near the cylinder gap when shooting. Very hot gas and occasional metal shavings escape from the cylinder gap when the round goes off. The faster the caliber and the larger the caliber, the more gas and flash. If the timing is off and a cylinder bore doesn't line up correctly with the forcing cone and barrel, you will get metal shaving.

    My Ruger Super Redhawk .454 Casull puts out a large flame from the end of the barrel and a large butterfly shaped flame from the cylinder gap when I shoot Hornady 240 grain XTP ammo. It is visible in bright sunshine. At night, it is quite awesome. Most of my revolvers and ammo only show a flame at night when shooting.
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    New Member Array rlggray's Avatar
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    It basically acts like a funnel. The cliff notes version is that it guides the bullet into the barrel from the cylinder.
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    Quote Originally Posted by WC145 View Post
    The only thing I'll add is that the barrel/forcing cone should not come in contact with the cylinder. There is a small gap there to allow the cylinder to move freely.

    The only exception to that that I can think of is the old Nambu revolver, IIRC, the action pushed the cylinder forward against the barrel when the trigger was pulled, eliminating the barrel/cylinder gap during firing.
    Nambu, the first name in how not to do it.
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    Senior Member Array ugh762x39's Avatar
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    Member Array Henry9008's Avatar
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    Quote Originally Posted by LimaCharlie View Post
    You never want your fingers or other body parts near the cylinder gap when shooting. Very hot gas and occasional metal shavings escape from the cylinder gap when the round goes off. The faster the caliber and the larger the caliber, the more gas and flash. If the timing is off and a cylinder bore doesn't line up correctly with the forcing cone and barrel, you will get metal shaving.

    My Ruger Super Redhawk .454 Casull puts out a large flame from the end of the barrel and a large butterfly shaped flame from the cylinder gap when I shoot Hornady 240 grain XTP ammo. It is visible in bright sunshine. At night, it is quite awesome. Most of my revolvers and ammo only show a flame at night when shooting.
    Same with my 4" Python when shooting hot magnum loads, such as the 125 gr load mentioned earlier.
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    Member Array M1911A1's Avatar
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    Quote Originally Posted by starlights View Post
    ...
    - how is the cone able to take that continual abuse?
    - is it a matter of the bullet being softer and the cone being harder?
    Yes.


    Quote Originally Posted by WC145 View Post
    The only thing I'll add is that the barrel/forcing cone should not come in contact with the cylinder. There is a small gap there to allow the cylinder to move freely...
    Supplementary Information:
    When that gap is too large, the situation is called "end shake" because the cylinder can move fore and aft in relation to the frame and barrel.
    The frequent result of "end shake" is that the cylinder will become very hard to revolve, after the first couple of shots.
    In an "end shake" condition, the fired cartridge "sets back," and protrudes rearwards from the cylinder, rubbing against the pistol's recoil shield. The friction of one or two set-back cartridges will bind-up the cylinder, and make revolving it difficult.


    Quote Originally Posted by WC145 View Post
    ...The only exception to that that I can think of is the old Nambu revolver, IIRC, the action pushed the cylinder forward against the barrel when the trigger was pulled, eliminating the barrel/cylinder gap during firing.
    The Russian Nagant revolver also has this, um, "feature."
    It was a Belgian invention!
    And it's useless.
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    Senior Member Array Bikenut's Avatar
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    Quote Originally Posted by WC145 View Post
    The only thing I'll add is that the barrel/forcing cone should not come in contact with the cylinder. There is a small gap there to allow the cylinder to move freely.

    The only exception to that that I can think of is the old Nambu revolver, IIRC, the action pushed the cylinder forward against the barrel when the trigger was pulled, eliminating the barrel/cylinder gap during firing.
    I wasn't aware the Nambu's cylinder moved forward to form a gas seal but I did know the Nagant 1895 revolver did.

    https://loadoutroom.com/thearmsguide...a-good-weapon/

    -snip-
    When the hammer comes back, the cylinder moves forward and over the forcing cone creating a gas seal for more velocity and later, the ability to suppress (silence ) the gun. -snip-

    I have one and some of the weird looking ammo plus the .32ACP conversion cylinder. Nice gun but so much extra complexity just to gain a few fps from the gas seal.

    Edited to add:
    M1911A1 beat me to it. I gotta learn to type faster.
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  16. #15
    VIP Member Array WC145's Avatar
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    You guys are correct, it was the Nagant revolver I was thinking of, not the Nambu. I must be getting old, can't keep all those old guns straight in my head anymore I guess.
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