Donkbet,
You're still having a problem in understanding the forcing cone.
Think of it as a funnel. Picture the funnel sideways, in profile. See the angle?
Its purpose is to channel a bullet into the barrel from the chamber.
The angle that everybody describing it on the other forum referred to is INSIDE THE BARREL, INSIDE THE CONE.
When a revolver's manufactured, there is a certain amount of looseness (or play) in the cylinder.
That's rotational (around) and front to back.
Both should be minimal.
The front to back movement in a direct line behind the barrel should be VERY minimal. If too much, it creates problems with endshake (too much fore & aft movement) which increases the gap between the cylinder and the forcing cone (undesirable) and can, if it goes too far, cause headspacing problems which can affect ignition.
Although it's not the true definition, you can think of headspace as the distance between the back of the cartridge and the frame's breechface (the part of the frame where the firing pin comes through).
SOME endshake is tolerable, too much is not, and it's measured with flat feeler gauges inserted into the barrel/cylinder gap.
Rotational play when the cylinder's locked is built in.
The less the better, but it's there.
The forcing cone is designed to deal with that slight rotational play.
If the barrel had no forcing cone with an INTERNAL angle, and the entire barrel was the same internal diameter from front to end, a slight rotational play in the cylinder could leave a chamber just enough out of line with the barrel's rear end at the moment of ignition to cause the bullet to hit the barrel slightly off-center.
That can cause material to be shaved off the bullet and forcefully spit out to whichever side through the barrel/cylinder gap.
Besides being a hazard to anybody who might be standing to that side, it can affect accuracy.
A given bullet will generally provide (other factors aside) its best accuracy if it enters the rifling as fully centered in the bore as possible.
The forcing cone is an internal cone-shaped section of the barrel at the rear that forces a slightly off-center bullet into straight-on alignment at the point where it meets the rifling.
The forcing cone is a funnel that's larger than the rifled section of the bore.
The forcing cone is larger than the opening in the front of the cylinder's chambers.
The forcing cone is larger than the bullet diameter.
The forcing cone "catches" a slightly off-center bullet as it transitions from the chamber into the barrel, aligns it with the bore, and prevents bullet shaving.
To do all that, as with any funnel or cone, it has to have an INTERNAL TAPERING ANGLE cut into the rear of the barrel.
That enlarges the opening, and removes the rifling inside the barrel at that forcing cone area, since it removes material INSIDE the barrel there.
The forcing cone is cut radially, using a spinning tool something like a cone-shaped grinder tip on the end of a hand drill (doesn't actually use a hand drill, is not cut by hand, just trying to explain in terms you can visualize).
That's what can leave those radial toolmarks in your cone.
I'll say again here that those radial toolmarks should not be there, certainly should not be so pronounced.
I have other Rugers (and other brands) where they are not.
Your gun will function. It may quite easily shoot well.
Ideally, the cone should have a surface free of machining rings, and most revolvers I own & work with do.
Yours is NOT typical, in my experience.
Consider what happens when you fire the gun.
The bullet slams into the wall of that forcing cone at high speed.
It doesn't come out of the chamber correctly centered in the bore, as mentioned above.
It WILL strike the cone's internal wall, somewhere (varies), on every shot fired, and the bullet will be very abruptly "re-directed" into line with the bore.
That means the bullet nose with be sliding along that section of the cone wall, however much & however briefly, on its path into the rifling.
Each tooling ring is an abrasive "shoulder" that the bullet hits during its travel.
Each tooling ring has the ability to scrape off minute bits of bullet surface on every shot you fire.
(Properly-done smooth cone walls tend to not do this.)
That rough ring abrasion will tend to be less on copper-jacketed bullets, but it can be much more if you fire a lot of lead.
Lead deposition, depending on how soft or how hard your bullets are & how much you shoot, can build up slowly or it can build up rapidly.
It can, and as I told you on the other site, I have experienced it, build up to the point of actually plating the cone walls with lead. In a Ruger, with a very badly done forcing cone.
When that happens, accuracy is affected.
As far as the degree of angle goes, forcing cones vary in depth (how deep or how shallow, how far inside the barrel they extend) and in degree.
There are industry specs set, there are gauges you can buy to determine whether a given cone falls within accepted tolerances.
Yours most likely has one in spec, as far as the depth & angle go.
It's a deeper cone than one on a Ruger .44 Special I have here, but that doesn't mean either is necessarily off.
The degree of INTERNAL angle on a cone can be altered by a gunsmith (or anybody buying the reamer from a place like Brownells), depending on what an individual owner wants to shoot.
One angle works better for strictly lead, another angle works better as a compromise for jacketed and lead.
Can't tell in your photos, obviously, how deep or what angle your cone is, but when others on the other forum told you it does have a cone cut into your bore (very apparent by the lack of visible rifling), they were correct.
I'll repeat- I would not accept a gun with those machining rings.
I have had a cone cleaned up, I have another one that's also poorly cut, with machining rings appearing about halfway into the cone, that needs to be cleaned up. And it will be.
If you're happy with your gun, by all means keep it.
The irregular machining and file marks on the face of the cone are a separate issue.
If squared off to the bore correctly, they're only cosmetic.
If not, that can affect accuracy and possibly uneven gas escape through the barrel/cylinder gap.
Hopefully, now you understand forcing cones a little better.
Denis
(Which shoots like a dream and is the most accurate handgun I have).
