Reading your pattern

If you're still deciding whether patterning is worth the trouble, start with Why pattern your gun — it covers what a pattern actually is and the five variables (gun, choke, barrel, ammo, lot) that make every combination its own animal. This piece picks up from there: a repeatable protocol you can take to the range tomorrow, and a guide to the four numbers that come out the other side.

A protocol you can actually repeat

The trap most shooters fall into is treating patterning as a one-shot science fair: one sheet of paper, one shell, eyeball the result, declare the choke "good," go home. That tells you almost nothing. Patterns vary shot to shot even from the same shell out of the same barrel, and a single sparse sheet is as likely to be lying to you as not. Build the session around two ideas instead: shoot at several distances, and put enough pellets on each first sheet to read it without squinting.

Start by patterning at 25, 30, 35, and 40 yards. For the first sheet at each distance, fire two shells into the same paper before you walk up to read it. The point isn't to validate the first shot with a second — it's signal-to-noise. A single shell puts a few hundred pellets on the paper, and at that count a normal pattern can read a touch sparse: gaps look bigger than they are, the dense core is hard to pick out, and the eye reaches for conclusions the data doesn't quite support. Stacking two shells onto one sheet roughly doubles the count, and the combined pattern's shape — the dense centre, the thinner shoulders, any real holes — jumps out at a glance. Once you've seen a combo of gun, choke, and shell read clearly that way and you trust what you're looking at, drop to one shell per sheet for the rest of the session.

Pick a primary testing distance based on how you actually shoot. Quick shooters who break the bird as soon as it's clear of the trap house tend to want the gun tuned around 25 yards. Late shooters who let the bird get out want it tuned closer to 35. 25 yards is a good starting point regardless of your style because the pattern is more concentrated there and easier to read by eye — you can see whether things are roughly working before you walk out to 40.

Use a rest for the first round. A gun stick, a sandbag, a fence post — anything that takes your wobble out of the result. A rested gun measures what the gun does. Once you have that baseline, take the same combination free-hand; the difference between the two tells you what your hold is adding.

The setup

Nothing fancy. A 40-inch square of butcher paper is plenty — big enough that even an opened-up 40 yd pattern lands fully on it. Put a 2-inch aim mark in the middle, pin the sheet to a backing frame at a known distance, and stand on flat ground. Aim at the dot every shot, so the offset between dot and point of impact (POI) is the gun's bias, not a moving aim.

Skip the pellet-by-pellet count

The traditional analysis step is to find the densest spot by eye, draw a 30-inch circle, count every pellet inside, and divide by the shell's nominal pellet count. It works, but it's tedious enough that most shooters do it once and never repeat the session that would actually answer their question. Patterning is about comparison — across distances, chokes, ammo lots — and comparisons need data, not one heroic count.

This is the part RangeVault does for you. The session uses two stickers per sheet — an aiming circle you place at centre before you shoot, and a QR label the app's computer vision uses to identify the photographed sheet. You can print both from RangeVault → Patterning → Stickers, or buy a sheet of pre-cut stickers at rangevault.io/#products if you'd rather not deal with paper alignment. The flow is short:

1. Hang a fresh sheet on the pattern board.
2. Place the aiming circle at centre — this is what you aim at.
3. Take your shot (or two, per the protocol above for the first sheet of each combo).
4. Walk down and stick the QR label on the sheet.
5. Open RangeVault → Patterning → New and follow the in-app prompts — the wizard walks you through photographing the label so the app can identify the session, then the pattern so it can measure it.
6. RangeVault detects the pellets, locates the POI, draws the 30-inch circle around it, and returns the four metrics this article covers next.

If you'd rather not use software, the manual version above gives you the first of the four metrics below — pattern density — and nothing else.

Four metrics, and what each one is telling you

Each of the four numbers RangeVault returns answers a different question about the pattern. The reference combo for the ranges below is 1⅛ oz #7.5 through a Full choke at 25–30 yards — a common clay-game baseline.

Pattern density (%)

The percentage of detected pellets that landed inside a 30-inch circle around the POI — (pellets within 30″ of POI) ÷ (total pellets) × 100. This is the number the choke-naming convention is built on; Full, Modified, Improved Cylinder and the rest are essentially labels for the density bands they produce at 40 yards. Three bands to expect in real-world results:

• 90–100% — tight, suits closer ranges or tighter chokes. Punishing if you mis-point.
• 70–90% — typical for general clay and field shooting.
• Below 70% — the pattern is opening up significantly. Usually the target is farther than the choke is tuned for.

Pellets in 30″ of POI (count)

The absolute count of detected pellets inside that same circle, round(density × pellet count ÷ 100). Density gives you the shape of the pattern; the count tells you whether there's enough shot in it to break a clay reliably. The absolute count is what you'd compare against a published expected range for your specific load. A 1⅛ oz #7.5 shell holds roughly 393 pellets; through a full choke at 30 yards, ~85% density puts about 330 in the 30-inch circle — well inside the in-pattern band for clay work.

Pattern diameter (inches)

The diameter of the smallest circle that contains 90% of the detected pellets — derived by taking the 90th-percentile distance from the centre of mass and doubling it. This is how forgiving the pattern is. For 1⅛ oz #7.5 through a Full choke at 25–30 yd, expect 24–32 inches. Below 24″ the pattern concentrates energy but punishes mis-pointing — a clay 18 inches off your line of aim might fly through clean air. Above 32″ it's more forgiving but trades density for spread, and eventually clays start slipping through interior gaps.

Evenness score (0–100)

How uniformly the pellets are distributed around the POI. RangeVault splits the 30″ circle into 8 angular sectors, counts the pellets per sector, and computes the coefficient of variation (standard deviation ÷ mean); lower variation produces a higher evenness score. Bands:

• 80–95 — excellent. A clay anywhere in the 30″ circle is statistically likely to take 3+ pellets.
• 60–80 — typical. Some sectors thinner than others, no glaring holes.
• Below 60 — notable gaps a clay could pass through unhit.

A high density with a low evenness is the classic "doughnut pattern" — plenty of pellets in the circle, just not where you needed them. Density alone wouldn't catch it; evenness does.

What a RangeVault analysis looks like

Two example sheets pulled from this shooter's RangeVault history, included to show how the four metrics actually surface in the app's output rather than to be compared against each other — the setups behind them are not matched. Figure 1 is a single-shell sheet; Figure 2 is a two-shell stacked sheet, which is the main reason the detected pellet counts differ by roughly 2×. Read each one on its own terms.

What to do with the POI offsets

The high–low and left–right splits RangeVault reports (the 69/31 and 43/57 style breakdowns) are the gun's signature. Look for consistency across distances. If every sheet for a given gun shoots a few inches high with a slight right bias, that's the gun — a stock/comb conversation, not a technique conversation, worth taking up with a fitter. If the bias jumps around session to session at the same distance, that's a hold problem and the fix lives in your mount. If it's drastic on one sheet and absent on the next, it's a one-off — pattern again before reacting.

A consistent vertical bias isn't always a bug. Many trap shooters deliberately want a gun that prints a few inches high so the bird stays visible above the rib as the trigger breaks, and have the stock fitted accordingly. Whether a high POI is "right" depends on you and your discipline — but knowing the number is the precondition for the conversation.

The first good pattern is the most valuable one you'll ever shoot

Numbers on paper today are useful. Numbers on paper today that you can compare against numbers on paper from two years ago are something else entirely. Once a gun, choke, and shell combination clicks — the density sits where you want it, the diameter is forgiving without being loose, the POI is honest, and the targets break — that pattern stops being a single result and starts being a baseline. Save it. Name it like you mean it: "Browning 825 / Full / Federal Top Gun 1⅛ oz #7.5 lot A". That sheet is the most valuable one you'll ever shoot, because it's the only one that captures exactly what "working" looks like for you.

Equipment changes are guaranteed. You'll buy a new gun. The shop will be out of your usual shell and you'll grab a close substitute. You'll switch from a competition load to something lighter for a field season, or the manufacturer will quietly retool a lot and the new case won't quite pattern like the old one. When any of that happens, the question isn't "is this new combination good in the abstract?" It's the much sharper "does this new combination reproduce the pattern I already know breaks targets?" This is where saving every pattern in RangeVault earns its keep — pull up last year's baseline next to today's sheet and the comparison is one screen, not a memory test.

Tune toward the baseline, not toward the textbook. If the new gun and new shells produce a tighter pattern than your saved sheet, open the choke a step. If they're looser, tighten it. If the density matches but the POI has shifted, that's a gun-fit conversation, not an ammo one. The recorded baseline tells you when to stop adjusting — when the new combination prints a pattern that overlays the one you already trust, you're done. You haven't invented a setup from scratch and hoped; you've reproduced a known-good result, which is a much shorter walk to confidence in the field.

The choke chart is a hypothesis, not an answer

The nominal percentages above are the starting hypothesis. They tell you roughly what to expect; the paper tells you what's actually happening. Treat the chart as a way to pick your first choke for a given distance, not as a substitute for confirming it.

When to repeat

Once when a gun is new to you. Once a year on the guns you keep shooting — barrels and chokes drift in subtle ways and a year is long enough to notice. And once whenever the ammo lot changes; the Why pattern your gun article explains why lot-to-lot variation is real even within a single SKU from a single manufacturer.