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Shotgun Cartridge Components Explained

Shotgun cartridges have similar components to that of a rifle cartridge.  The components of a shotgun cartridge are:

  • The Projectile
  • The Case
  • The Wad
  • Propellant 
  • The Head
  • The Rim
  • The Primer


  1. The explosive center of the shell.
  2. Firing pin hits primer.
  3. Powder in primer ignites.
  4. Ignites the propellant in the shell.


  1. Fast burning material that creates a gas expansion in the shell.
  2. This propels the shot down and out the barrel.


The Shell Case is what houses everything.

The common sizes of Shotgun Shells are

  • 10 Ga
  • 12 Ga
  • 20 Ga
  • .410

What does the “gauge” of a shotgun shell mean?

  • Gauge originated when cannons and muzzleloaders were common.
  • The spherical lead ball was a fraction of a pound.
  • A 10 Gauge ball was 1/10 of a pound.
  • A 12 Gauge ball was 1/12 of a pound.
  • The bore was a 10, 12 or 20 Gauge bore… this carried over to the modern shotgun.
  • A smaller number meant a bigger ball, which meant a bigger bore.

What size is a .410 shotgun.

  • .410 is designated for a caliber number.
  • It is slightly larger than a 40 caliber cartridge.
  • The bore is about 10 mm.

Uncommon shotgun shell sizes

  • 4,8,16,24,28,32
  • These are either not common or considered obsolete.
  • The 10 gauge is becoming less common as well due to Lengthening and strengthing of 12 Ga shells.

Common Shell Lengths for Shotguns

  • 2 ¾, 3, 3 ½ inch
  • Shotguns will have the length etched on them.
  • You may go shorter than the shotgun length, but not longer.

The Head

The head is the brass around the base of the cartridge.

The Rim

The rim is the small brass ring on the bottom of the shell.

  • Allows ejection of the shell by the action of the shotgun.
  • Keeps the shell chambered correctly.

The Wad Column

Made up of 3 components

  1. The Gas Seal
  2. The Cushion
  3. The Shot Cup

Some wads are designed to be all three in one.

The Gas Seal

  • This is designed to keep the expanding gas from moving behind it.
  • This keeps all expansion and momentum going forward.

The Cushion

This is the shock absorber

  • It prevents sudden violent expansion of gas from warping the shot (soft lead)

Shells have different propellant and shot quantities.

  • The cushion also takes up the empty space so the shell is standard length.

The Shot Cup

The cup houses the shot and keeps it together as it travels down the barrel.

  • It is slotted, so once it leaves the barrel, it tears away from the shot.
  • This allows the shot to travel freely in air.

The Projectile

There are two basic projectile types.

  1. Shot, or pellets
  2. Slugs

Shotgun Slugs

Shotguns were designed to shoot the ball type shot from the old muskets.  These are called “Pumpkin Ball” slugs.

  • Since then, slugs have gotten much more sophisticated with design.

Some of the benefits of slugs today:

  • These new designs allow us to bring some “rifle” qualities to shotguns.
  • All the force is focused to one spot.
  • This allows for greater impact or penetration on large game.

There are 9 main slug types


  1. Pumpkin Ball
  2. Brenneke
  3. Foster
  4. Saboted
  5. Wad
  6. Plumbata
  7. Steel
  8. Wax
  9. Cut Shell

Pumpkin Ball Slug

  • One of the first slug shots.
  • Round lead ball, just smaller than the bore.
  • Not too accurate
  • Limited range of about 25-50 yards

Brenneke Slugs

  • Designed in late 1800s
  • Had a rifling of the slug
  • The rifling was not at all for spin and added none
  • It reduced surface area on the barrel, reducing friction, and raising exit velocity.
  • It had stabilization problems due to being a solid slug.

The fix?

  • Designed with small piece of wad that stays attached to the back
  • Purpose of this: created drag needed for slug stability.
  • It also helped a little with gas sealing.

Brenneke Slugs have a range of 50-75 yards.

Foster Slugs

  • Designed during the great depression.
  • Hollowed out rear putting mass at the tip for stable air flow
  • Meant to be used in a smooth barrel with a choke.

Foster Slugs also have rifling on them.

  • Similar purpose as the Brenneke Slugs.
  • Still for surface area
  • Not for spin effect

The hollowed design and rifling make the foster:

  • Extremely manageable in choked barrels
  • Give it a range of about 75 yards

Saboted Slugs

The big item here is the wad cup.

  • The jacket coveres the entire slug.
  • It catches the rifling of rifled shotguns adding spin
  • This gives it a range up to 330 yards when fired from rifled shotguns.

An interesting bit of information is that the sabot was designed for smoothbore guns

Wad Slug

The wad slug is also called a key slug.  It isn’t anything fancy about it.

  • It is a mix of the foster slug and saboted slug.
  • The slug is hollow at the back and is filled with a key (lead line) in it.
  • The range of a wad slug is about 75 yards… same as the foster.

Why would you use a wad slug or key slug?

It is designed to fit in a typical “SHOT” wad. This means it can be reloaded using standard reloading equipment.

Plumbata Slug

There are two designs of the plumbata.

One type has wadding designed to fit in the tail end.

  • It stays with the slug through flight for stability.
  • Sabots can be placed into the slug.

Another design wraps around the base of the slug

  • It engages groves into the slug acting as a saboted slug.
  • It is called an “Impact Discarding Sabot”

Steel Slugs

These must be saboted so they don’t damage the barrel.

I argue that I don’t know much about shotguns, especially steel slugs

I don’t think there is much benefit to these.

  • It is expensive
  • It can be outperformed by a specific rifles where it matters:
    • Dense brush
    • Disabling vehicles

Wax Slugs

Wax slugs were used during the great depression.

How to make a wax slug:

  1. Remove shot from shell
  2. Slightly cut the shell back a little
  3. Melt paraffin wax
  4. Add shot to the wax
  5. Spoon the wax back into the shell
  6. No crimping is necessary due to wax buildup

I wont use wax slugs unless highly necessary because it builds up in the barrel.

If you use it, you MUST clean your shotgun extremely well afterwards.

Typical range of a Wax Slug is about 50 yards.

Cut Shell Slugs

Cut shell slugs were also used during the great depression.

How cut shell slugs were made:

  1. Cut a groove around the shell dead center of the wad.
  2. Cut the groove nearly through the shell all the way around.
  3. The shell fails prior to the crimping.

Cut shell slugs were usually made “in the field” when larger game showed up.

Problems with cut shell slugs:

  • Higher chamber pressures
  • Some of the shell could stick in the barrel

Shotgun Shot

If I go into detail here, it could bore you, so I will try to keep it quick.

There are 2 different basic types of shot.

  1. Buckshot
  2. Birdshot


  • Meant for larger animals.
  • Normal sizes range from 4 to 1, then 0 to 000, then Tri-ball 12 and Tri-ball 20
  • Smaller buckshot actually has a good failure rate.
    • I would use 00 or larger for buckshot.
  • Buckshot does a pretty good job for home defense
    • Buckshot larger than number 2


  • Useful for fowl and smaller game.
  • Birdshot runs from 9 down to 1, then B to BBB, then T, TT, F, FF

I will have a chart on the shownotes, but allow me to address a few common animals that birdshot is used for.

  • 7 ½ for Dove and Pigeon
  • 6-7 for grouse
  • 6 for squirrel
  • 5 for pheasant
  • 4-6 for turkey
  • 6-2 for duck (using tungsten) the smaller shot is for using decoys.
  • 4-B for duck (using steel)
  • BB or BBB for Geese

shotgun shell

shotgun shell

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Ken is addicted to fitness and mountain biking. He is such a thrill seeker, people are starting to be concerned!He enjoys MTBing, Hiking, Climbing, Geocaching, Orienteering, Weight Lifting, and Wilderness Survival.

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