There's a whole can of worms here, folks. One maker may call a .015 constriction Light Modified, another Skeet II, another Modified, and so ad nauseam. Basically the names run in the same order,so relative choke's easy to figure out.
Start with the bore diameter, 12 gauges these days run from .720 or so to the way overbored .750". Stan Baker even made an .800" Big Bore barrel.
A choke with no constriction would be bore diameter and called Cylinder choke. A skeet choke might be .004 or .005 tighter or it might be bore diameter. Then Improved Cylinder at another .004 or .005" and so on to maybe 40 Points of Constriction, AKA .001" each.
Actually, the chokes were classified by the percentage of pellets hitting inside a 30" circle at a predetermined distance, traditionally 40 yards for all but the teeny 410, which gets patterned at 25 yards. 50% was considered Improved, Cylinder, 75% Modified, etc. We use the constrictions as an easy way to distinguish various percentages.
I wouldn't trust ANY markings without shooting patterns with the ammo of choice. Loads can vary those percentages by more than an increment of choke, and a long forcing cone can mimic a tighter constriction.Sometimes it seems like the phase of the moon, stage of the tide and if I'm getting enough fiber affect the pattern also. There's NEVER been two identical patterns shot in all the long history of scatterguns.
Here's an emperical test to see if the
load/choke/cone combination can do a given mission. Having the right sized shot is a given here.
If the patterning board shows at least one pellet in every two square inches of target, with few holes, the setup oughta work if we do our part. Or, use a clay target, and if it cannot fit over less than three holes in the target, good. Some folks have cut 4" discs from plexiglass to do this.
Here's a guideline for how much choke to use on a particular shot in SC or trap, dial it in by repeatedly shooting the same flight path,changing chokes tubes, and stopping when you're getting smoke frequently. Then back off one increment. Smoke is wasted density, so the next choke more open should bust the clay nicely and still have a good spread. Needless to say, this works best for fairtomiddlin' shooters.
A variant on this is done by some top clay shooters. they practice with tight chokes and compete with more open ones.
Skeet needs no choke,near as I can tell. While there used to be Skeet I and II chokes, modern ammo patterns tighter from a cylinder bore than 1960s stuff does from a Skeet choke. Some skeet guns have negative constriction at the muzzle, and work well.
HTH, ask if there's still foggy places....
PS, may G*d Bless all Jarheads...
