There are many different sizes of shot, shot itself being the metal spheres that make up the projectile end of a shotshell. This is because, as in the disciplines of rifle and pistol shooting, there is a different application (hunting, target practice, self defense, etc.) suited for the use of a different sized bullets and sizes of shot. Much like certain bullet sizes and weights are used for any number of purposes they are well suited to, certain shot sizes are perfect, due to their size and weight, for the relevant application for which they are used. For instance, one does not use #2 lead shot on quail- it is simply overkill. Conversely, one does not use #8 on ducks, because that is sure to maim the duck and not inflict a mortal hit.
Excluding the scheme used in non-toxic shot, the smaller the number listed for a size of shot, the larger the shot will be. To illustrate, #5 (.120" dia.) shot is larger than #9 (.080" dia.). The larger the shot, considering the same velocity, the more energy it contains- it hits harder in the same distance as the smaller shot. It simply has more mass. What this means is that the size of the game comes into play when selecting the proper size shot. You wouldn't use too large a size of shot, for fear of damaging the meat. You also wouldn't use too small a size of shot, for fear of crippling the animal.
Certain shotgun shooting sports, such as skeet shooting, use #9 size shot (fairly small). The targets are close, the chokes are fairly open; the amount of effective shot is higher since they are smaller (meaning you can fit more into a load by weight) and it has enough energy to break the target. Trap shooting, on the other hand, has distances that are occasionally double that of skeet and thus one would pick a larger size of shot to make sure of a target break. When you go up a size in shot, you lose an x amount of pellets per ounce. This can be a factor in determining what is the best size shot to use, also.
Distance to the target plays a large part of how to select the proper shot size. If you are expecting or can lure the target in closer, then a smaller size than ordinarily used can be loaded. If the game is not coming in close, it is time to break out the larger size of shot. As an example, if one knows that they can call in ducks fairly close, one may use #6 or #7.5 sized shot. If the ducks are not coming in close, one would choose to use #4 or #5 sized shot.
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Shot can be broken down into two main camps- lead shot and non-toxic shot. As a result of this division, there are some sizes available in lead shot that are not available in non-toxic shot and vice versa. While there is some overlapping, there are a few different sizes offered in the non-toxic scheme for different applications. This has to do with the size of shot and the density of material from which it is created.
In what follows, I am going to list each grouping of shot- buckshot, lead shot and steel shot (the predominant of the non-toxics)- and list their diameter in inches and for what purpose to which they would be used.
Buckshot
Buckshot is the largest of all shotgun pellet sizes. These are usually meant for the taking of larger animal, such as a buck deer, elk and so on. Buckshot is also used in the elimination of predators such as feral dogs, coyotes and foxes. Buckshot is lead shot (occasionally plated), though larger and in its own category.
- #000 BUCK .360" dia. — The largest of all buckshot sizes, this is meant for deer and elk.
- #00 BUCK .330" dia. — (The famous "double ought buck" one may hear). Deer sized game.
- #0 BUCK .320" dia. — Close large game load; self defense load.
- #1 BUCK .300" dia. — Close large game load; self defense load.
- #2 BUCK .270" dia. — Feral dog, fox, coyote.
- #3 BUCK .250" dia. — Feral dog, fox, coyote.
- #4 BUCK .240" dia. — Feral dog, fox, coyote.
Lead Shot
Lead shot can come plated in nickel and copper, adding better ballistics to the load in question. This does not seem to alter the size of the shot; however, sometimes the nickel plated shot can be larger, due to the manufacturing process. Please note; all sizes of lead shot are no longer allowed as hunting loads for waterfowl in the United States. I merely list what they were used for in an attempt to show the trend of size versus game taken.
- #2 .150 dia. — Goose.
- #4 .130 dia. — Goose.
- #5 .120 dia. — Ducks, pheasants.
- #6 .110 dia. — Ducks, crows, rabbits.
- #7 .100 dia. — Not readily available; dove, partridge, rabbits.
- #7 1/2 .095 dia. — Trap Shooting, dove, chukar, pigeon.
- #8 .090 dia. — Quail, pigeon, dove.
- #8.5 .085 dia. — Quail.
- #9 .080 dia. — Quail, skeet shooting, starlings and blackbirds.
- #10 .070 dia. — Small pest removal, such as snakes. There are no known shotshells loaded with this size of shot.
- #11 .060 dia. — Small pest removal, such as rats. There are no known shotshells loaded with this size of shot.
- #12 .050 dia. — Known as "dust" or rat shot in the industry, this is meant for small pest removal. Rats. There are no known shotshells loaded with this size of shot.
Steel Shot
Please note that steel shot does come in other sizes; #2, #3, #4, #6, #7. They are of the same diameter as their lead counterparts. #2, #3, #4 would be OK duck loads; #6 and #7 would be acceptable for dove and quail in addition to target shooting. Also, please recall that the difference in density between lead versus steel is great; therefore, larger sizes of steel are needed to deliver the same foot pounds of energy required to humanely kill an animal.
- #F .220" dia. — Long range geese (excess of 40 yards).
- #TT .210" dia. — Ibid.
- #T .200" dia. — Medium range geese (excess of 30, but no more than 40 yards).
- #BBB .190" dia. — Ibid.
- #BB .180" dia. — Ducks.
- #1 .160" dia. — Ducks.
Note: The information contained within is accurate insofar as it is representative of the shot sizes available in the USA. There are some variations on some shot sizes in other countries, such as Great Britain and Mexico but they are not very large differences.
Sources:
http://www.remington.com
http://www.ballisticproducts.com
http://www.winchester.com