What is "Forcing Cone Lengthened"

[bushmaster1313]

What does this mean in a used gun ad for an 1897?

 

[4thPointOfContact]

The chamber of a shotgun is larger in diameter than the the barrel.
The portion of the barrel in front of the chamber which narrows to the diameter of the barrel is the forcing cone.
The angle can be abrupt, or it can be made more gradual .... which lengthens it.
Lengthening the forcing cone is said to reduce distortion of the payload and (I think) perceived recoil.

 

[webbee]

Here's a nice article on forcing cone lengthing.
The reason that an 1897 might need this done is to accomodate modern shells. Originally the forcing cone was cut short for paper hulls which needed to seal closer than plastic shells do. Pattern adjustment is a more modern approach too.
The selling point being that the buyer doesn't have to pay to have it done.

 

[artee]

What an awesome graphic 4thpointofocntact!

 

[cfullgraf]

...and (I think) perceived recoil.

Yes, lengthening the forcing cones will reduce perceived recoil. Not like the difference between a 12 ga 1-1/8 oz load and a 12 ga 7/8 oz load but the difference is noticeable.

 

[Jim_100]

Wow,
I know why I study here. Nice replies.

 

[Leadhead]

One thing that baffles me about lengthened forcing cones is,

If it's so great why don't the manufacturer's just make them with longer forcing cones?

 

[PapaG]

I've done a dozen or so with a reamer we made some time back. I notice absolutely no difference in recoil nor can anyone else who shoots them. I often put a non-lengthened cone barrel on a gun, let a friend fire it, then switch to the lengthened cone barrel. Asked which one has less recoil, they are only fifty-fifty on picking the lengthened one. My studies, and born out by some work done by Greener over a hundred years ago, show that the main reason is to improve patterns by reducing shot deformation as it more easily transitions through a long cone than a short one. Often, at the other end of the barrel, a longer taper in the choke also begets better patterns.
I've machined "sweat" on chokes for guns with shot off or shortened barrels and by making the taper relatively long (often a half degree per side of taper) and a parallel at the end which just the same length as the desired shot charge to be shot gives excellent patterns, very dense and even in the full chokes I tried.
Shotgun chokes, patterns, cones, overboring, and the like are very intricate and non-definite sciences. That is why Briley, Baker, and the others make the big bucks for their work.

 

[JNewell]

There's some discussion here. It can improve patterns on any shotgun, not just old paper-hull barrels. I highly recommend Mike Orlen's work.

 

[oneounceload]

Longer forcing cones main reason for being is to reduce pellet deformation upon ignition - it tends to gently squeeze the pellets down to bore size. (Gently being a relative term). That seems to lessen the initial pressure which many believe helps lessen the perceived recoil. It does nothing for actual recoil - that's another animal.

As to why it isn't done to every gun - cost comes to mind. Target guns are usually done - not all, but most. More labor means higher cost.

 

[Leadhead]

I don't know much about cutting out the chamber and forcing cone but if it makes a difference and I was making shotgun barrels I'd buy or make some new cutters and reamers and improve my design and market it as such.

I don't see how it would cost that much more to manufature once the tools were bought, and if it is indeed better for the shot then the improved barrel and improved sales should/would pay for the change in tooling..?

Maybe the difference is just not that noticeable and it's just a way for customizers to squeeze out the last percentile of improvement out of the barrel....

 

[oneounceload]

If the reamers aren't set up exactly correct, then you can potentially get issues with concentricity - again, I agree it SHOULDN'T be hard to do, but there are reasons why they aren't

 

[Youngster]

I've heard it said that the surface finishing on a lengthened forcing cone is critical and if poorly done can do more harm than good as far as patterning goes.

Merely cutting a long cone may not add much in the way of production costs, but trueing and polishing the result to the needed degree is likely cost prohibitive when you're talking low and mid grade shotguns.

 

[Red Cent]

I have done a number of forcing cones including the 1897. This procedure will spread the pressure curve from a spike with a normal forcing cone to a longer curve with a lenghtened forcing cone. You will always have the same amount of pressure but it can be spread over a period of time with the lengthened forcing cone. The factory forcing cone is abrupt with a sharp angle. When you ream the cone you stretch out the angle into an almost an unnoticeable cone therefore reducing the abrupt entry of the wad/shot into a gradual entry into the remainder of the barrel.
The procedure itself is not as complicated as some make it. The forcing cone reamer somewhat self aligns unless you have a real problem with holding a long bar straight in a small openeing.
Combine the lengthened forcing cone with backboring and you can improve the pattern capabilities of a shotgun and help with "perceived recoil". The concentricity of backboring is much more difficult than the forcing cone.
A modern trap shotgun like a Kolar always has a long lengthened forcing cone and is backbored out to/up to .740. The nominal ID of a cylinder bore 12 gauge is .729.My SKB Trap Combo and my Remington STS Premier Comp has the factory lengthened forcing cone and the SKB has the .740 factory backbore.
All informed and pocket book able clay shooters will own such a shotgun. I do and, at least, I am informed.

 

[Red Cent]

Youngster, I use two items to finish a forcing cone job. First I use a two blade brake cylinder hone to smooth the cones. Secondly, I use the "balls on a stick" with their proprietary oil to further polish the job. Sometimes, the metal produces some weird lines and I use a dowel rod with a strip of fine sandpaper to put the finishing touch on the job.

 

[JNewell]

reduce pellet deformation upon ignition - it tends to gently squeeze the pellets down to bore size.

This also translates to shot that flies a little truer and patterns a little tighter.