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Author Topic: Shotshell Basics  (Read 2439 times)

Offline Gunscribe

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Shotshell Basics
« on: February 14, 2008, 03:37:03 PM »
Loaded rounds are correctly referred to as shotshells. The empty casings are correctly referred as hulls.

Shotshells consist of five basic parts;
  • 1) Hull - the paper or plastic brass ended container that holds the rest of the components. Note: some hulls are also made entirely of plastic or brass.

    2) Primer - the cap in the base of the hull that when indented by the firing pin ignites the powder.

    3) Powder - a solid propulsion fuel that when ignited by the primer turns to a gaseous form. Gas takes up more space than the solid it represents and it is the expansion pressure in gas form that expels the shot from the hull.

    4) Shot - the multiple projectiles that are expelled from the barrel that impact the target.

    5) Wad - the cushion between the powder and shot. In modern shotshells this is sometimes referred to as a shot cup. The shot cup base forms the wad and the sides of it go all the way up the inside of the hull creating a cup for the shot. The sides of the shot cup are cut length wise in four places so that soon after leaving the muzzle the sides will separate themselves from the shot by opening like a flower petals and falling away. 

Gauge v. Caliber

Fowling pieces were invented long before the first settlers arrived on the shores of America. In the Old Country the number of  round balls the diameter of the bore it took to equal one pound determined the gauge. 12 round balls = 12 gauge, 20 round balls = 20 gauge.

Even though a pound of 12 is still a pound of 20, in this case less is more. Since it takes less 12 gauge round balls to make the pound the 12 balls are bigger around than the 20, so the inside diameter of the 12 is larger than that of the 20.

The .410 has caused a lot of confusion in its time since it is the newest of choices available for scatter gunning and the .410 designation is that of a caliber (i.e. like the .308 or .243).

Shot size

The shotgun is likely the single most versatile firearm available. It can be loaded with a wide variety of shotshells for just about any purpose from trap shooting, small/big game hunting to personal defense.

In determining shot size the larger the number the smaller the shot size. 

Number nine (#9) shot is the smallest that is readily commercially available and is usually only used for trap, skeet and dove hunting.

#8 and  #7 1/2 are larger than nine and see much use in the field for small game such as quail, pheasant and rabbits. It also sees some use on the trap/skeet ranges as well.

#6, #5 and sometimes #4 are the preferred choice of many for pheasant and rabbit as well. There are some knowledgeable professionals that recommend #4 shot for shotguns kept in the home for the purpose of personal protection.

All of those listed above are the most common lead shot sizes commercially available and the usage noted is only a traditional guideline.

For hunting waterfowl anytime and even other game in designated areas the use of Non-toxic shot is required. I will not delve into that in this post as the complexities require it to a be a stand alone post.

Shotshells for self defense and slugs for hunting large game also need their own stand alone posts.


Choke in a shotgun barrel refers to an amount of tapered restriction inside the muzzle end of the barrel. The amount of restriction determines the effective range of the shotgun. The tighter the restriction the farther the effective range.

  • Cylinder Bore - is no restriction at all. A cylinder bore barrel is the same diameter the entire length. Maximum shot spread is achieved in the shortest distance with this type of barrel. It is generally accepted that for hunting applications 15 to 20 yards is the effective range.

    Improved Cylinder - is the slightest restriction readily available. The humane effective range recommended for hunting with this choke is about 25 yards.

    Modified - Many will argue that if only one choke were to be available this one should be it. The effective humane hunting range for this restriction is generally accepted to be 30 yards (35 maximum).
    Full - this is the most restrictive of all of the standard chokes available and provides an effective range of 40 to 45 yards.
Yes, I know there are other chokes, but they are usually for specialized types of hunting such as waterfowl, turkey and other game that I commented above deserve their own post.

Maximum effective range is defined as the distance that 90% or more of the shot from one shell impacts inside a 30 inch circle. With a cylinder Bore choke this would be about 20 yards and so on with a full choke being about 40 yards. Every shotgun is different and these distances are only an approximate guide line (re: Patterning below)

To visualize what a choke does;

Imagine a group of people several rows deep walking shoulder to shoulder (shot in a shot cup) down a hallway (barrel). When they arrive at a set of double doors (Modified choke) that open away from them to the outside of the building, they have to "tighten up" their formation to fit through the doorway (choke). Now imagine if that double hallway (barrel) only had a single width door (Full choke) at the end of it. 

In older shotguns the choke and barrel were all one piece and the amount of choke was stamped on the barrel. Adjustable chokes were available that were soldered to the muzzle of the barrel. These were affectionately referred to as "Dial-a Ducks" and could be twisted from no choke at all to a full choke setting by using the graduated marks embossed on them.

In recent years "removable choke tubes" have become the normal. Using a special wrench to install and remove them they are screwed into the inside of the muzzle. Some sit flush with the muzzle others extend past the end varying distances.

Shotshell Length

Shotshells for 10, 12 and 20 gauge (the most common in use today) come in three lengths; 2 3/4 inch, 3 inch and 3 1/2 inch (except the 20 gauge). As will be noted under the Ballistics heading the longer versions do not necessarily have more "power" than the standard load. They only have more shot.


Specialty loads aside the single biggest difference between the gauges is the size of the bore. 7/8ths ounce of shot in a 12 is still 7/8ths ounce of shot in a 20.

A look at a ballistics chart for standard shotshell loadings (2 3/4") also reveals that the velocity and energy difference between the 12 and 20 gauge is negligible, meaning that they each hit just as hard with approximately the same speed at the same distances.


In many offerings the 1 1/8th ounce 12 gauge load does not have any more velocity or energy than a 7/8ths ounce 20 gauge. The advantage is the 12 gauge load has more pellets in the pattern.

Standard loadings for the 12 and 20 are normally 1195 fps, 1250 fps and 1300 fps.

It should also be noted that for most standard hunting loads a 3 inch 12 does not hit any harder down range than a 2 3/4 inch 12. As many will attest that does not apply to the butt end of the shotgun though.

A three inch 12 will have more shot than a 2 3/4 inch 12 so it takes more powder to propel that extra weight at the same velocity. The perceived "painful recoil" advantage of the 3 inch is that there is more shot in the pattern thus making it more lethal provided it ends up at the target.


Not all shotguns will impact the shot pattern centered on the target, even those brand new right out of the box.

Patterning a shotgun can shed a ton of day light on why you have been missing.


If your shotgun is hitting to the right and you barely have the proper lead on a target crossing from the right you will likely miss. If your shotgun is hitting low or high it probably doesn't matter how many times you get the lead correct.

To pattern a shotgun set up a large (at least 40x40 inch) piece of paper at the maximum yardage for the amount of choke you have installed. Aim for a spot you have marked in the exact center and fire a couple of shots. Now draw a 30 inch circle (15 inches from center all the way around the arc) and see where the densest part of your pattern is. High? Left? Right? Low? Center? Does that explain some things?

Adjusting the impact point of a shotgun barrel is not a kitchen table gunsmith project. Essentially there are two choices; Pay a professional or use the knowledge to adjust your point of aim the next time your shooting at moving targets.     
« Last Edit: February 15, 2008, 11:09:25 AM by Gunscribe »
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