Explain shotgun chokes to me...

[Super-Dave]

Can you explain all of the different shotgun chokes. That is list the tightest choke to the widest choke in order. I am very ignorant about the different chokes and would like to remedy this.

Also if you can list what each choke is best to use for.

[zippy13]

Check out this page by Briley (http://www.briley.com/index.asp?PageAction=Custom&ID=51). Is this what you wanted to know?

[darkgael]

Good question but a very long answer. I can't do it justice as reams of paper have been written on this subject. Books.
In general terms, a choke is a tightening or a constriction on the bore of a shotgun barrel. A 12 ga. bore is nominally 0.729" in diameter (or more or less, depending on who you talk to). Let's go with that. That diameter barrel is referred to as "Cylinder bore". On a barrel that has been tightened at the muzzle (more complex than that) so that the diameter is 0.722" (0.007" constriction), the choke is called "improved cylinder". Tighten it by 0.011" and you have a "modified" choke, by 0.036" and it's a "Full" choke.
Chokes change the speed at which a shot charge opens or spreads. A useful rule of thumb is that a load of shot fired through a cylinder choked barrel will open at the rate of two inches a yard. A full choke will open at one inch per yard. That is the most general guide.
Pete

[Super-Dave]

Thanks that helped.

It does not look like IC does much more than cylinder. Based on the data at the site I would not think switching from cylinder to IC would gain much. However it looks like a switch from cylinder to modified is significant.

[darkgael]

Despite that "rule of thumb", you can't really know how a choke will work until you pattern the loads that you are going to use in your gun.
Pete

[BigJimP]

Zippy gave you a great link Dave.

I disagree with you Dave - switching from Cyl to IC can make a big difference at about 30 yards - especially if the target is edge on toward you / and the reason you pick a specific choke is to put an effective 30" pattern on the target or bird at the kill range.

When I'm hunting or shooting sporting clays with an O/U for chokes I carry 2 Skeet, 2 Imp Cyc, 2 Mod, 1 Imp Mod and 1 Full - and I select chokes based on what I expect the birds to be doing over the dogs / or what the break point kill range is for a clay target.

But not all chokes are created equal / you have to use a bore gague to measure your bore - then measure the choke / the markings are an indication / but can vary a little. Until you take the gun to a pattern board - and see what a barrel / choke combination is really doing - at the kill range, you're just guessing. You can't judge it by shooting at moving targets.

[oneounceload]

Super Dave - here's some links to sites about chokes:

http://www.hallowellco.com/choke_chart.htm

http://www.fieldandclays.com/expert_chokes.htm

http://www.briley.com/index.asp?PageAction=Custom&ID=51

[true_pair]

tube sizes for 12ga
Cyl .730
Skeet .725
I.C .720
Modified .710
Imp.Mod. .705
Full .700
X-Full .690
Turkey .680

From Carlson's Choke tube site