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Discussion Starter · #3 ·
It would be interesting to know if the bullet is compressed or "distorted" during ignition and its initial movement into the bore? What kinds of pressures are exerted upon the sides of the forcing cone, and does it compress or flex during ignition? What kinds of tolerances are acceptable, and what kinds of tolerances can lead to failure? What is the history of the forcing cone, and how has it developed over the years as the revolver has evolved?

Do steel, stainless steel, and titanium forcing cones have different metrics, and are these differences significant?

I had always thought revolver chambers were perfectly aligned with the barrel--and the very idea of a forcing cone--a "funnel" for a hot speeding piece of lead exploding from a brass case--is pretty darn interesting. /forums/images/graemlins/wink.gif

Yep, these are academic questions, but "learn for the sake of learning" I always say.... /forums/images/graemlins/smile.gif
 

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The forcing cone is a critical part of a revolver, but is little understood or even much noticed, including by many pro gunsmiths.

The critical dimension is the outer edge of the cone. Taper or depth is not really that important.
If the outer mouth of the cone is too little, the gun is inaccurate and will spit bullet metal.
Too big and accuracy suffers.
The difference between too big and too little is tiny.

Forcing cones are cut with a special cutting tool that works down the bore.
A rod in inserted into the barrel and a tapered cutter is attached.
The cutter, (which comes in various taper or degrees) is pulled into the barrel and the handle is turned to cut the cone.
A special plug gage is used to gage the cone.

When the cone gages correctly, the cutter is removed and a matching brass lapping head is installed. This is coated with grinding compound and the cone is lapped to a smooth finish.

Various degree taper cutters and laps can be used to set up a gun for firing various bullets.
A longer taper can be used for lead bullets, a shorter works for jacketed.
The factories use a good compromise taper.

How a bullet reacts with a cone depends on the gun.
The older design Colt revolvers were famous for better accuracy, and a lot of this was due to Colt's famous "Bank Vault" lock up.

In the Colt, when the trigger is pulled back, the cylinder is forced into near-perfect alignment with the forcing cone and bore, and locked tightly.
Since the bullet enters the cone and bore perfectly aligned, there's little bullet deformation.
The down side is, the guns must be hand fitted and adjusted, and if they get slightly out of order, they simply don't work properly.
Also, these hand fitted guns are very expensive to build.

New Colt's like the Mark III/King Cobra work like all other revolvers like S&W, Ruger, Taurus, etc.
In these models, the cylinder is deliberately allowed to be slightly loose when the trigger is pulled back.
This allows the bullet entering the forcing cone to force the cylinder into alignment.

The problem is, since the bullet never enters the cone and bore aligned, the bullet is deformed more, and accuracy suffers.
The good part of this is, the guns are cheaper to build and will work even when the action is not in proper adjustment.

Forcing cones do take a beating, both from the bullet impacting on it, and from the erosion effect of the super-heated burning powder which has a white-hot sand blaster effect.

Forcing cone erosion is seen mostly in Magnum calibers, especially in those firing hot, light weight bullet defense loads.
A load that's both the most effective defense load AND the hardest on forcing cones is the .357 Magnum, 125 grain, jacketed hollow point load.
These hot, high velocity loads can erode cones, and in the case of the .357 S&W Model 19 and 66 "K" frames guns, it can cause cracks or even broken cones.

The erosion and damage is actually metal fatigue caused by blast damage from bullet impact, the white-hot gasses, and the sand blast-like effects of the powder.
A cracked forcing cone usually means a barrel replacement, since it's impossible to determine how far forward the metal fatigue and cracks go.

Theoretically, stainless and Titanium barrels should handle this better, but stainless seems to be just as prone as carbon steel.
Titanium might be better, but barrels aren't actually made of Titanium.

When the early Titanium guns were being introduced, the manufactures discovered a little "quirk" about Titanium: A rifled Titanium barrel tends to UN-rifle.
Over a period of time, Titanium tends to attempt to return to shape, especially under heat and pressure, and they found that rifling actually "blurred" and "faded".

For this reason, today, all Titanium guns actually have a stainless steel barrel liner pressed into a Titanium outer "shroud".
Look at a Titanium revolver, and you'll see the rifled stainless liner in the barrel.

So, the revolver forcing cone is a LOT more than just some kind of a funnel in the barrel.
 

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ColtAgent / Dr. D, Thank you for inspiring our brains. Great question from a newbie.
 

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The November Cowboy Cronicles had a telling article about gun blow ups. SAA's which have had reduced power bolt/cylinder stop springs installed run the risk durning rapid fire of the cylinder bypassing the bolt. If the firing pin engages the edge of the primer causing ignition with the barrel/forcing cone out of allignment with the cylinder, the bullet with all the expanding gases behind it has no where to go until the top half of the cylinder and the topstrap are blown away. I use to think that a no charge/double charge reload was the only way to trash a gun. Clearly, barrel/forcing cone- cylinder misallignment caused by light bolt springs is another key to catastrophic failure.
 

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E= MC2.....................
Majic is the closest..................

In an "open breach" system a forcing cone is required to allow for the bullet "jump, this is of course NOT necessary in a "closed breach" system.
Alas, just a "funnel" to help ease the bullet down its path of projection.
Way too heavy for us everday folk, need to have engineering, metallurgical degrees to "see" the whys and the wherefores. /forums/images/graemlins/wink.gif
 

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Thank you dfariswheel.
I for one thoroughly enjoyed your post. I'd like to see more in depth explainations for some of the stuff we tend to take for granted.
 

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I cracked a MK3 Nickel Lawman with a hot blue dot load and a 125 grain bullet. The load was slightly under max. in only one <a href="http://www.coltforum.com/forums/?page=book">book</a>. I later found out that it was above max. in most other books. The reason it probably cracked was because I must have fired about 75 rds in less than 5 mins. and it must have been really hot. It now sports a 5 in. offical police barrel that I bought off of ebay for $10. I believe with any .357 it is important to let the gun cool between heavy loads. Mike
 

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Nice discussion DFariswheel,

Thanks for taking the time to post this one.
 

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Discussion Starter · #12 ·
[ QUOTE ]

In the Colt, when the trigger is pulled back, the cylinder is forced into near-perfect alignment with the forcing cone and bore, and locked tightly. Since the bullet enters the cone and bore perfectly aligned, there's little bullet deformation. The down side is, the guns must be hand fitted and adjusted, and if they get slightly out of order, they simply don't work properly. Also, these hand fitted guns are very expensive to build.


New Colt's like the Mark III/King Cobra work like all other revolvers like S&W, Ruger, Taurus, etc. In these models, the cylinder is deliberately allowed to be slightly loose when the trigger is pulled back. This allows the bullet entering the forcing cone to force the cylinder into alignment.


[/ QUOTE ]

How does the bullet entering the forcing cone force the cylinder into alignment? Is it the bullet itself, or is it the pressure of the expanding gasses?

Do shot shells, with tiny shot rather than bullets, properly force the cylinder into alignment?

Does the Colt Agent Second Issue align in the fashion of newer Colts and S&W, or does it function like the older Colts with near-perfect alignment?

Thanks.

P.S. DFariswheel: If you wrote a book on revolvers with more of this kind of information I'd add it to my library, and I believe many others would too.
 

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I'll play (over my head) while Dr. D rests his fingers.

If you do a Google search on "forcing cone", you will find most of the information is shotgun/shot oriented. Apparently pellet deformation and pattern degradation is one related concern in shotguns.

The Agent is an "older" Colt with regard to action.

It would seem the bullet would still be partly in the chamber when it begins to enter and be affected by the alignment with and taper of the cone and any resulting alignment would be mechanical. I suspect that shot in a revolver cartridge would not cause alignment but would be more subject to "splatter" (my term) somewhat like shaving. JMO
/forums/images/graemlins/cool.gif
 

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In order:

It's the bullet itself that forces the cylinder into alignment on the newer Colt's and all other brands.
The problem is, the bullet never enters the forcing cone centered like the older Colt's, so the bullet impacts on the side of the cone.
This causes distortion, which reduces accuracy at least slightly.

Most shot shells I've seen have the shot packed in plastic capsules.
When the capsule exits the muzzle, the capsule ruptures, releasing the shot.
Since the shot is still in the capsule when it passes from the cylinder into the barrel, the plastic also aligns the cylinder to the bore, like a bullet does.
The problem here is, the softer plastic deforms even more than a lead bullet, but this means nothing with a shot round.
With the older shot cartridges in which the shot was packed loose in the case, I would assume there would be alignment, even though the shot column would not be a solid mass, but the loose column of shot might cause the cylinder to "wander" from side to side.

All the Colt "D" frames like the Agent have the old-style Colt actions that align and lock the cylinder with the bore.
This is a major reason why the "D" frame Colt's were the Cadillac of snubby revolvers, and were noted for their better accuracy over other brands.
 

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[ QUOTE ]
It would be interesting to know if the bullet is compressed or "distorted" during ignition and its initial movement into the bore?

[/ QUOTE ]
Yes a bullet is distorted due to physics. The base distorts as it begins to move because the nose is resisting to move. The base distorts some more as the nose slows when it enters the smaller portion of the forcing cone, but the base wants to continue moving at the same speed. As the bullet goes thru the forcing cone it is swaged down to size eliminating the diameter distortion of the base. You will also have some distortion as the bullet doesn't hit the forcing cone square to the centerline. The bullet then distorts some more as the rifling is impacted on it. It wants to resists the lateral spin it has to make plus the grooves that are cut into it.
A bullet leads a quick, violent life just getting out of the barrel.
 

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Majic is ablolutely correct. There is even more distortion of the bullet as the hot powder gasses tend to vaporise a tiny portion of the base. Additionally the bullet is compressed front to rear, by the force of the powder gasses pushing against it's base while friction, air pressure and other forces try to stop it's foreward motion. The bullet does in fact have a short violent life.
 
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