Shotgun Choke and Shot String

When a shotshell is fired from a shotgun, the pellets leave the barrel and begin to spread or scatter. The farther the pellets travel, the greater the spread of the group of pellets (shot) both in length and diameter. This spread is called the shot string.

choke: The degree of narrowing at the muzzle end of the shotgun barrel
shot pattern: The spread of shot pellets after they hit a non-moving target
shot string: The three-dimensional spread of shot pellets after they leave the barrel

Effect of Shot Deformation and Air Resistance on the Shot String

• When a shotshell is fired, the pellets at the front of the group are more deformed and more affected by air resistance (drag). These pellets:
  • Tend to slow down and spread out from the rest of the pellets.
  • Eventually move towards the back of the shot string and determine the length and diameter of the shot string as shown on the next page.
  • May not have enough speed to result in a clean kill if they hit the target.
• The pellets that are in the middle or back of the group as they leave the barrel are less deformed and encounter less air resistance. These pellets are more likely to maintain their speed and to result in a clean kill when they hit the target.

Effect of a Shotgun’s Choke on the Shot String

• To control the shot string, shotgun barrels have a choke, which will affect the shot pattern when the shot string hits the target. Read more about how to pattern a shotgun in Chapter Three.
• Your distance from the target determines the choke you need. The choke of a shotgun determines shot string only. It has no bearing on shot speed (velocity) or distance (range). That is, the choke does not alter the shotgun’s power—it just controls how tight or spread out the pellets will be at a specific distance.
• The spread effect of the most common chokes is illustrated below, showing how many pellets will hit within a certain area at different ranges.
  • Cylinder choke is an unconstricted barrel. The shot string spreads quickly. This is a good choice for quick upland birds like quail, woodcock, and others that hold tight before flushing.
  • Improved Cylinder choke has a slight constriction. It allows the shot string to spread fairly quickly. This is a good choice for squirrels, rabbits, pheasants, and other upland game at relatively close ranges.
  • Modified choke has moderate constriction. The pellets stay together longer, making the shot string denser and more useful at longer ranges. This choke is used often when dove hunting and when using steel shot to hunt for ducks or geese. There is also an Improved Modified choke that is slightly tighter than Modified.
  • Full choke has tight constriction. The shot string holds together even longer, making this choke good for squirrels, turkey, and other game shot at 40-yard and longer ranges. Turkey hunters sometimes use Extra Full or Turkey choke for even denser patterns at long range.

The illustrations of shot strings represent the full load of pellets ar a particular instant in time after a shotshell is fired.

Steel Shot

Steel shot is slightly lighter than lead shot of the same size. Also, steel shot is harder than lead, so the individual pellets stay round, keeping the pattern tighter.

Some hunters use steel shot one or two sizes larger to make up for the difference in weight from lead shot. Others use the same size steel shot or even smaller steel shot to get more shot into their patterns. You should pattern your shotgun with various loads of steel shot before hunting waterfowl with it.

Effective pattern density is the key. Maximum pellet counts spread evenly across a 30-inch circle are best. Full chokes generally produce poor patterns with steel shot.