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Shotgun Gauges and Cartridges

4 gauge
Used mostly by market hunters in the late 19th and Early 20th century in the United States. European Big Game hunters used them in Africa
8 gauge
Has some industrial application, used by market hunters in Late 19th early 20th century. 1 3/4 oz to 2 1/4 oz loads at 1200 fps. Shell lengths 3,3 1/4, 3 3/4, 4 inch.
10 gauge
There has been a resurgence in the popularity in this gauge because of the US regulations requiring the use of non toxic shot for hunting waterfowl. Particulary steel shot.
12 gauge
Most common gauge shell lengths 2 1/2 obsolete, 2 3/4, 3 inch magnum, 3 1/2 inch magnum. Most new 12 gauge shotguns sold today will be chambered to take 2 3/4 inch and 3 inch shells. The 3 1/2 inch magnum shotguns are generally used with steel shot for hunting waterfowl.
14 gauge
The 14 gauge was somewhat common in the last two decades of the late 19th century and into the early twentieth century. Shell lengths 2, 2.5 and 2 9/16 th inches. Bore diameter .0693 inches
16 gauge
The 16 gauge is basically obsolete but it still it enjoys some popularity particularly in the United States due to the number of working guns chambered for it. From time to time some gun manufactuers still chamber the occasional gun for this gauge just for old times sake.
20 gauge
This is the second most popular gauge after the 12 Gauge. Current shell lengths available today are 2/34 and 3 inch magnum shells.

All currently manufactured 20 gauge shells are some shade of yellow. A number of individuals over the years have found to their dismay that if a 20 gauge cartridge is put into a twelve gauge barrel, that the shell will slide just far enough into the barrel to allow a twelve gauge shell to be loaded behind it. If the gun is fired under this circumstance, the 20 gauge shell will act as a barrel obstruction and may itself go off if the primer is struck. Generally the end result is that the shotgun is destroyed and the user is injured.

24 gauge
The 24 gauge is obsolete but there are still quite a few functioning shotguns chambered for this round. Ammunition for this gauge is still manufactured in Europe.
28 gauge
Although the 28 gauge is used by a few upland game hunters, it is most often seen used in gauge specific skeet tournaments in the U.S. The 28 gauge's low recoil makes it an ideal target cartridge to teach children and women of small stature to shoot a shotgun. Cartridges however tend to be expensive, hard to find and for reloaders case life is short, sometimes as few as 3 firings. Itís small 3/4 oz shot payload makes it unattractive choice for most upland bird hunters.
32 gauge
Primarily a European Chambering, loaded ammunition is still available for this fairly obscure gauge. Standard load is 1/2 ounce of shot
410 Bore
This is the only shotgun gauge that is commonly identified by its bore diameter, it is actually a 67 gauge. Used primarily by skeet shooters, it also has some popularity among small game hunters. A small payload of shot and generally tight patterns make it an unforgiving gauge for both hunting and clay target shooting. As a chambering for a youth shotgun, I believe that it is a very poor choice albeit a common one. A brief review of the history of the 410 Gauge

Shotgun Bore Diameters by Gauge

Gauge Bore Diameter in inches
4 0.935
8 0.835
10 0.775
12 0.730
14 0.693
16 0.670
20 0.615
24 0.579
28 0.550
32 0.526
410 0.410

Shotshell Gauges, Dram Equivalents and Velocities

Gauge Shell Len. Dram Eq. Shot Wt. Vel.
10 3 1/2 4 1/4 2 1210
10 3 1/2 4 3/4 1 5/8 1285
-- ------ ---- ---- ----
12 2 3/4 4 1 1/2 1305
12 2 3/4 3 3/4 1 1/2 1260
12 2 3/4 3 3/4 1 1/4 1315
12 2 3/4 3 1/2 1 1/4 1275
12 2 3/4 3 1/4 1 1/4 1220
12 2 3/4 3 3/4 1 1/8 1365
12 2 3/4 3 1/2 1 1/8 1310
12 2 3/4 3 1 1/8 1200
12 2 3/4 2 3/4 1 1/8 1145
12 2 3/4 3 1/4 1 1290
12 2 3/4 3 1 1250
12 2 3/4 2 3/4 1 1180
-- ------ ---- ---- ----
16 2 3/4 2 3/4 1 1/8 1185
16 2 3/4 2 1/2 1 1165
-- ------ ---- ---- ----
20 2 3/4 2 1/2 1 1165
20 2 3/4 2 1/2 7/8 1210
-- ------ ---- ---- ----
28 2 3/4 2 1/4 1 1205
28 2 3/4 2 1/4 7/8 1250
28 2 3/4 2 1/4 3/4 1295
28 2 3/4 2 3/4 1200
28 2 3/4 1 3/4 5/8 1160

Lead Shot

Lawrence 5 lb Chilled Shot Bag

In terms of reloading there are four basic types of lead shot.

Drop Shot
Nearly pure soft lead with less than one half percent of Antimonal content. Prone to deformation. Rarely obtainable as there seems to be little demand for it.
Chilled Shot
Will be somewhat harder than drop shot with a antimonal content of 1 to 2 percent. Usually the least expensive option
Magnum Shot
Will contain 4 to 6 percent of antimony.
Plated Shot
Typically soft lead shot plated with nickel or copper. Developed before the widespread use of plastic wadcolumns when shot would be deformed by scraping along the barrel. Magnum shot will generally perform better at a lower cost.

Birdshot and Buckshot Sizes

American Shot Pellet dia. Avg. Number Pellets British Shot
Size# (Inches) per ounce (Lead) Size#
Dust 0.0400 4560 -
12 0.050 2385 -
10 0.070 870 -
9 0.080 585 9
8 1/2 0.085 495 8
8 0.090 410 7 1/2
7 1/2 0.095 350 7
7 0.100 299 6
6 0.110 223 5
5 0.120 170 4
4 0.130 135 3
2 0.150 90 B
1 0.160 71 BB
B 0.170 59 -
BB 0.180 50 A
BBB 0.190 42 AA
T 0.200 40 AAA
4 Buck 0.240 21.3 -
3 Buck 0.250 18.7 -
2 Buck 0.270 14.9 -
1 Buck 0.300 10.9 -
0 Buck 0.320 9.0 -
00 Buck 0.330 7.6 -
000 Buck 0.360 6.4 -
To determine the diameter of shot in hundredths of an inch for shot sizes smaller than #B in the American system subtract the size number from 17. For example size 8 1/2 would be 17 - 8.5 which is 0.085 inches or 8.5 hundredths of an inch.


Density of Lead Shot

When reloading shotgun shells, lead shot is generally measured volumetrically rather than by weight. A question that often arises is, what is the density of lead shot. Frequently I seen online sources quote the figure of 11 grams per cubic centimeter which is wrong. This is the density of solid lead not of lead shot

Lead shot is in fact a mass of tiny spheres with a fair amount of air space within the mass. The larger the shot size, the more air space contained within a given volume. For size 8 chilled lead shot the density is about 6.32 grams per cubic centimeter or 3.47 ounces per cubic inch. Most charge bars or shot bushings on shotshell reloader are calibrated to dispense a given weight of #8 or #7 1/2 chilled shot. If larger shot is being used then shot charge thrown will be slightly light. If smaller shot is being used then the weight of the shot thrown by the measure will be slightly greater than with larger shot.

Shot Size #9 #8 #7.5 #5 #2
Grams per CC 6.41 6.40 6.32 6.30 6.24

For example the volume of a 1 1/8 oz shot bushing calibrated for size 7 1/2 shot is slightly less than 1/3 cubic inch. The weight of #9 shot chilled shot thrown by this same bushing will be little more than 1/64 of an ounce heavier than the stated value of 1 1/8 ounce. This amounts to about an additional 9 extra pellets. Generally this discrepancy is of little concern to the reloader but it can be to a competitive skeet shooter who risks disqualification from a shoot if he or she uses cartridges which contain more pellets than the rules of the competition allow. As a result of this, many manufacturers offer charge bars for skeet shooters which are designed to measure out the correct weight of #9 shot.

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