Forcing Cone & IC

[9mmMike]

I have read many posts here that recommend lengthening the forcing cone of an 870.
Does it matter if my shotgun has an IC or not?
I have heard the IC referred to as a modified choke but I thought that chokes were removable and the IC, as I understand it, is a permanent mod to the barrel.
Please be kind. I am still learning about my first shotgun here.
Thanks,
Mike

[Dfariswheel]

The IC is the Improved Cylinder choke. It doesn't matter if the choke is a permanent or screw-in choke. The Modified is another, "tighter" choke.

As I recall the chokes, both permanent and screw-in are:
Cylinder bore (no choke at all)
Improved Cylinder
Modified
Full

There are probably a couple of other special purpose chokes also.

[K80Geoff]

The forcing cone is as the breech end of the barrel. If you have it altered it will not affect the choke which is at the muzzle end. Chokes are either fixed, which means the barrel has a built in choke. Or interchangeable , which means the choke screws out of the end of the barrel and can be replaced with different chokes.

IC means Improved Cylinder and is usually around .10 hundreds constriction. the amount of constiction can vary from manufacturer to manufacturer.

Briley is a major manufacturer of chokes and their choke constrictions are as follows for 12 GA:

cylinder= no constriction
Skeet (Sometimes called skeet in)= .05 hundreds constriction
Improved Cylinder = .10 hundreds constriction
Light Modified (sometimes called Skeet 2 or Skeet out)= .15 hundreds constriction
Modified = .20 hundreds constriction
Improved Modified = .25 hundreds constriction
Light Full = .30 hundreds constriction
Full = .35 hundreds constriction
Extra full = . 40 hundreds constriction

Geoff Ross

[9mmMike]

Thanks guys. This is a print and file for me.
Mike