I found the following description of chokes from the Briley webpage:
“Shotgun chokes were designed to control pattern diameters at different yards. What is a pattern? It is just the grouping of the pellets at a given yardage. This grouping is called a pattern and is measured by a circle diameter. This particular circle must have certain efficiency. In other words, it has to have a certain number of pellets in a given area (called distribution) for it to be labeled an efficient pattern. It is that easy! However the confusion starts when we label them and you try to figure out what to use and when”.
Probably the biggest challenge we have as shooters is to decide which chokes to use. There are many thoughts on the use of chokes. Some people have what are called ‘fixed’ chokes and they are permanently in their gun, never to change. Then there are the chokes that are ‘flush’ to the gun and there are ‘extended’ chokes (sticking out of the gun.)
Some shooters change their chokes at every station depending on the presentation and then others just occasionally change their chokes. It really depends on the shooter.
Here is generally how shooters use each of these chokes
| Percentage of Constriction Based on Distance | |||
| Choke | 20 Yards | 30 Yards | 40 Yards |
| Cylinder | 80% | 60% | 40% |
| Skeet | 92% | 72% | 50% |
| Improved Cylinder | 100% | 77% | 55% |
| Modified | 100% | 83% | 60% |
| Improved Modified | 100% | 91% | 65% |
| Full | 100% | 100% | 70% |
Super-Full and Extra-Full Chokes – This has very tight constriction and a dense pattern, delivering approximately 80 percent of a cartridge’s total pellets in a 30″ circle at 40 yards.
Full Choke – This has tight constriction and a dense pattern, delivering approximately 70 percent of a cartridge’s total pellets in a 30″ circle at 40 yards.
Modified Choke – The modified is characterized by less constriction than full choke, delivering approximately 60 percent of a cartridge’s total pellets in a 30″ circle at 40 yards.
Improved Cylinder Choke – Even less constricted than modified, the improved cylinder distributes approximately 50 percent of a cartridge’s total pellets in a 30″ circle at 40 yards.
Cylinder Bore – No constriction and distributes approximately 40 percent of a cartridge’s total pellets in a 30″ circle at 40 yards.
Skeet Choke – A specialty choke that sends approximately 50 percent of a cartridge’s total pellets in a 30″ circle at 25 yards. This type is designed to deliver optimum patterns for close-range skeet shooting.
Shoot ‘em up!
Linda Henson