$ cd ..
// ~/playground/pellets

Pellets

What's in the shell

Pick two loads. See every pellet in each one, drawn to the same scale, with the count. Then put both patterns on a bird at 40 yards and see what the extra pellets buy you.

$ ./pellets --compare # edit anything; estimates are marked EST
In the shell, then poured out
— LOAD A
— LOAD B
The cutaways are a mock-up. The pellets and the height of the shot column are to scale, in the shortest 12 gauge hull (2¾, 3 or 3½ inch) the load fits. A stacked load has the smaller shot against the wad and the bigger shot on top, the way steel stacks are loaded. A cutaway shows one slice of the column, so the powder and wad are for show and the count is in the pile: every pellet in that shell. The ring is a dime.
LOAD A
fps
%
Pellets in the shell
—
One pellet
— in
Weighs
— gr
LOAD B
fps
%
Pellets in the shell
—
One pellet
— in
Weighs
— gr
One simulated shot from each load, 40 yards, on a 5 foot board
LOAD A
In the 30 in circle
—
On the bird, this shot
—
Each pellet arrives at EST
— fps
Carrying EST
— ft·lb
LOAD B
In the 30 in circle
—
On the bird, this shot
—
Each pellet arrives at EST
— fps
Carrying EST
— ft·lb
The dashed ring is the 30 inch pattern circle. Bright dots hit the bird. In a stacked load the bigger dots are the bigger shot. Click the board to move the bird off centre, the way most shots really land, or drag it. Wings and tail feathers don't count.
Head to head
Load A Load BB against A

The math, and every assumption it makes 
pellet diameter  = (17 − shot number) ÷ 100 inch
pellet weight    = sphere volume × density
pellet count     = payload ÷ pellet weight
share in circle  = 1 − exp(−15² ÷ 2σ²)      σ = pattern spread, inches
energy           = grains × fps² ÷ 450,240   ft·lb
  • Counts. Pellets are treated as perfect spheres. Densities: steel 7.86, bismuth 9.6, lead 11.1 (hardened shot, lighter than pure lead), tungsten blend 12.0, TSS 18.1 g/cc. That lands within about 2% of the per-ounce tables printed in loading manuals. Your box can differ by a few pellets. Makers round, and pellets aren't all the same size.
  • Stacked loads split the payload in half by weight, one half in each size. That reproduces a tested 1¼ oz BB and #2 load, which held 123 pellets. Makers don't all publish their split, so a given box can differ. Both sizes are drawn from the same pattern curve. In a real shell the big shot and the small shot may not pattern alike.
  • Speed and energy at range are an estimate. Each pellet is a smooth sphere in standard sea-level air, with the drag a sphere has at each speed. Real pellets are rougher, and the back of the shot string is slower than the front. Checked against published 40 yard figures, it runs about 3% low.
  • Pattern percentage is the classic number: the share of pellets inside a 30 inch circle at 40 yards. The choke sets it for lead: Cylinder 40, Improved Cylinder 50, Modified 60, Full 70. Steel and TSS get 10 points more, the tungsten blend 5, because hard shot patterns tighter. If you have patterned your gun, type your own number.
  • The pattern itself is a round bell curve about the point of aim, as wide as that percentage requires. Spread grows a little faster than distance (distance to the power 1.3), which matches the old tables: a Full choke holds 70% at 40 yards, about 50% at 50, about 30% at 60.
  • The birds are life-size side views built from a few ovals. "On the bird" counts pellets on the body, neck and head. It is not a count of pellets in the vitals, and it says nothing about what a pellet does when it gets there.
  • Real patterns are patchier than this. Every gun, choke and load combination throws its own. A pattern board and a box of shells beats any simulation.
1

The number is the size, backwards

Bigger number, smaller pellet. Each step is one hundredth of an inch.

American shot sizes follow a rule. Take the number away from 17 and you have the diameter in hundredths of an inch. A #2 is 0.15 inch. A #5 is 0.12. A #9 is 0.08. A half size sits halfway: the #1.5 in some steel goose loads is 0.155.

Above #1 the numbers run out and the letters start: B, BB, BBB, T, F, each one another hundredth bigger. The rule is the same for every material. A steel #2 and a lead #2 are the same size.

Every shot size, to scale
Your two loads are ringed. Diameters in inches.
Note: A small step in diameter is a big step in weight, because weight goes with the cube. A #2 is only 25% wider than a #5 and almost twice as heavy.
2

Same size, different weight

An ounce is an ounce. What changes is how many pellets it takes to make one.

Steel is about 30% lighter than lead for the same size. So an ounce of steel #2s has more pellets in it than an ounce of lead #2s: 125 against 88.

That is also why steel loads use bigger shot. A light pellet loses speed faster, so you go up two sizes to get the punch back, and the count comes back down. Steel #2 and lead #5 is the comparison this page opens on, because that is the trade a duck hunter and a pheasant hunter each make.

Light shot also takes up more room. The steel in a 1⅛ oz load stands about an inch tall in a 12 gauge bore. The same weight of lead is under three quarters of an inch. That is why steel duck loads grew into 3 and 3½ inch hulls.

Pellets per ounce
Computed from diameter and density. Your two loads are outlined. Click any cell to load it into A.
Note: TSS is the far end of this. At 18 g/cc a #9 weighs about what a lead #7½ does, so a 2 oz turkey load carries over 700 of them.
3

What a pellet has left at range

A round ball is a terrible shape for flying. Shot loses half its speed in 40 yards.

Air drag pushes on a pellet's frontal area. The pellet resists with its weight. Area goes with the square of the diameter and weight with the cube, so a bigger pellet has more weight behind every bit of area. So does a denser one. Both hold their speed better.

Energy goes with the square of speed. A pellet that arrives at half its muzzle speed arrives with a quarter of its energy.

Energy per pellet, muzzle to 60 yards

Note: Extra muzzle velocity is mostly gone by the time it matters. The faster a ball goes, the harder the air pushes back, and above the speed of sound the drag roughly doubles. Change a load's velocity by 100 fps above and watch how little the 40 yard number moves.
4

Count is what fills the pattern

The choke decides how wide the cloud is. The count decides how many holes are in it.

A choke doesn't add pellets. It decides what share of them land inside a 30 inch circle at 40 yards. Full puts about 70% of a lead load in the circle. Improved Cylinder puts about half.

Past 40 yards the cloud keeps opening and the same pellets cover more paper. The gaps between them grow until a bird can sit in one. More pellets in the shell push that distance out. A tighter choke does too, at the cost of a smaller cloud up close.

Pellets inside the 30 inch circle, 20 to 60 yards

A stacked load spends the budget both ways. Half the payload goes to a bigger size for energy and half to a smaller size for count. Pick a second size under "Stacked with" above and compare it with either size on its own. The count lands between the two, and so does everything else.

Note: Both halves have to hold up. Enough pellets to put several on the bird, and enough energy in each to matter when it gets there. Small shot wins the first and loses the second. That is the whole argument about shot size.
  1. size
  2. density
  3. count
  4. pattern
  5. energy on arrival

An ounce of shot is a budget. You spend it on many small pellets or a few big ones.

$ ./recoil → what the same load does to your shoulder

$ cd .. → more interactives