Musket ball size chart: identify lead shot by weight and diameter

Lead balls are among the most common finds in a ploughed field. Most look identical. They aren’t. Weigh one properly and it will usually tell you roughly what kind of gun it was cast for, and sometimes which century.

How to measure a musket ball

Weight comes first. The Portable Antiquities Scheme (PAS) guide to shot calls weight “vital” because it gives you the bore and calibre, while the maximum diameter can be less reliable. Glenn Foard’s Battlefields Trust guidance says the same thing: weight is quick, objective and has a known error.

What you need:

• Digital scales reading to 0.01 g. Foard recommends recalibrating them at the start of every session. That gives a working accuracy of about ±0.05 g.
• Digital calipers reading to 0.01 mm. Measure the width across the mould line, avoiding any offset. Then take the depth at 90° to it. Skip the sprue and any impact damage.
• A note of the findspot. A ball with no location is just a weight. A ball with a grid reference is evidence.

Don’t clean it first. Treasure Trove Scotland asks finders not to clean finds at all, and the surface marks described below are part of the evidence.

What “bore” means

Bore is the old way of stating calibre: the number of balls cast from one pound of lead. In the PAS guide’s words, “12 bore = 12 balls to the pound.” So a smaller bore number means a bigger ball.

The pound is fixed in UK law at exactly 0.45359237 kg, so the sum is simple:

bore = 453.59 ÷ weight in grams

Foard also gives a formula for the ideal diameter of a perfect lead sphere of a given weight:

diameter (mm) = 20 × (0.021 × grams)^⅓

We used both to build the chart below. The diameters are ideals. Real balls rarely match them exactly.

Musket ball size chart

Weight = 453.59 g ÷ bore. Ideal diameter from Foard’s formula for a perfect sphere of lead; inches converted from mm. Highlighted rows are the single typical sizes the PAS gives for 17th and 18th-century guns. Matches use the PAS shot table.

Why your ball may not match the chart

Foard lists the usual culprits. Air bubbles, or a cold mould that never filled, make a ball lighter. Worn or badly registered moulds leave an offset that makes it wider. Snipping off the sprue removes a little lead. Firing removes more: experimental case shot lost as much as two bore.

So use the ranges, not a single row.

Which gun? Musket, carbine or pistol

The PAS guide gives typical weights for the main weapons. Its table is based on Courtney (1988) and Foard (2008).

Another PAS record (DENO-E7E565) quotes Harding’s weight ranges for shot from Easton Maudit. They make a useful wider net:

The overlaps are real. A 23 g ball could be a 17th-century carbine ball or an 18th-century one. The PAS is blunt about it: individual 17th-century shot can’t usually be assigned precisely to a weapon.

Civil War or later?

Lead shot arrived in the mid-15th century. But the PAS guide says most shot found in England and Wales is likely to be mid-17th century, the era of the Civil Wars.

The best clue is variety. Firearms of the 18th century were far more standardised, so a wide spread of sizes from one site points to the Civil War. Casting flashes on several bullets in a group suggest a 17th-century date too.

Edgehill shows the pattern. Foard found 12 bore was by far the most common calibre there. Balls from the battle, analysed and reported in a 2010 Cranfield thesis, were 12 bore: about 37.9 g and a theoretical 18.51 mm across.

Later shot looks different:

• Drop shot from shot towers, which date from the late 18th century.
• Conical bullets, which are 19th century. In Britain they turn up on rifle ranges used from the 1860s, often by the Rifle Volunteers.
• Belted bullets, also 19th century, made for a two-grooved rifle.

Surface clues

A ball’s surface can show how it was made and what happened to it.

• Sprue. Where the neck of lead was cut off. One nip of the cutters leaves two facets, two nips leave four, and a knife leaves one. A cavity near the sprue is shrinkage from cooling.
• Mould line and casting flash. A seam or thin fin round the middle, from the two halves of the mould.
• Set-up bands. When several balls were loaded at once they squashed into each other, leaving a band round the ball and flat faces where they touched. The PAS says these are fairly common.
• Gas erosion. Facets or shallow grooves tapering the back of the ball, where gases escaped past a loose fit.
• Worm scars. A worm, or wormer, was a corkscrew on the end of a ramrod used to pull shot out of a barrel. Scars can be rounded holes with screw threads. The PAS has no certain examples on its database yet.
• Slugs. Largely cylindrical bullets, cast that way or trimmed or hammered down from balls. Their weight and width matter more than their length, and Foard notes that weight still gives the original calibre of a hammered slug.

Bite marks? Often claimed, rarely convincing. Foard says definite bite marks are rare, even though soldiers routinely held bullets in their mouths ready for loading. The PAS adds that most “bitten” balls on its database are just battered by the plough, and corroded lead tastes sweet, so animals may have gnawed some. As for “bite the bullet”, the evidence links it more to enduring punishment beatings than battlefield surgery.

Worked example

Two balls recorded on the PAS database (record DENO-E85C15) weigh 32.04 g and 32.05 g, with diameters of 17.8 mm and 18.2 mm. They are dated AD 1600–1800 and show set-up marks.

Run 32.04 g through the sums. That’s 14.2 bore, with an ideal diameter of 17.5 mm. The nearest typical size is the 18th-century musket ball at 31 g (14½ bore). But one or two balls can’t settle the date. That’s why the record keeps the range wide, and why groups matter more than single finds.

Record it

A musket ball is not Treasure on its own. It still has value as evidence, especially if you have a group.

• England and Wales. Take it to your local Finds Liaison Officer. Anything that might be Treasure must be reported within 14 days of finding it, or of realising it might be Treasure. Wreck material goes to the Receiver of Wreck within 28 days.
• Scotland. All significant portable antiquities must be reported to Treasure Trove Scotland. Their own advice on what to report: “Everything! Well, most things.”
• Battlefields. On a known battlefield the PAS says detecting should arguably only be done in partnership with the Battlefields Trust. The Trust can help get the most information out of a site.

And always get the landowner’s permission first. Our permission letter template covers that, and what counts as Treasure explains the reporting rules in England and Wales. There are separate guides for Scotland and Northern Ireland. For more find guides, open the Find ID drawer.

FAQ

How do I tell what gun a musket ball was fired from?

Weigh it and convert the weight to bore (453.6 divided by the weight in grams). Then compare it with the period ranges: 17th-century musket balls are typically 38–41 g (11–12 bore), and 18th-century musket balls about 31 g (14½ bore). A single ball can rarely be pinned to one weapon, so treat the result as a likely match, not a certainty.

What size is a musket ball in mm?

A perfect 12-bore lead ball (37.8 g) works out at about 18.5 mm across. An 18th-century musket ball of about 31 g is about 17.3 mm. Real balls vary because of air bubbles, sprues and badly matched moulds, which is why weight is the better guide.

How can I tell a Civil War musket ball from a later one?

Look at the group, not one ball. 17th-century shot came in a wide variety of sizes and often shows casting flashes from the mould. 18th-century firearms were far more standardised. A spread of sizes on one site points to the Civil War.

Do I have to report a musket ball?

A single musket ball is not Treasure in England and Wales, but the Portable Antiquities Scheme records finds like this, and groups of shot are especially useful. In Scotland, all significant portable antiquities must be reported to Treasure Trove Scotland. On a known battlefield, the PAS says detecting should arguably only be done in partnership with the Battlefields Trust.

Are conical bullets musket balls?

No. Conical bullets are 19th century. In Britain they turn up on rifle ranges used from the 1860s, often by the Rifle Volunteers.

Sources

Every figure in this guide comes from one of these. We checked each one on 1 November 2026.

1. Webley, R. “Shot (including musket balls, cannon balls and bullet moulds)”. Portable Antiquities Scheme finds guide, including its shot-size table based on Courtney 1988 and Foard 2008. finds.org.uk/shot
2. Foard, G. (2009) Guidance on Recording Lead Bullets from Early Modern Battlefields. The Battlefields Trust. www.battlefieldstrust.com/media/762.pdf
3. Portable Antiquities Scheme record DENO-E7E565 (lead shot, with Harding’s Easton Maudit weight ranges). finds.org.uk/database/artefacts/record/id/266828
4. Portable Antiquities Scheme record DENO-E85C15 (two lead balls, 32.04 g and 32.05 g). finds.org.uk/database/artefacts/record/id/266837
5. Miller, D. P. (2010) Ballistics of 17th Century Muskets. MSc thesis, Cranfield University. dspace.lib.cranfield.ac.uk/server/api/core/bitstreams/8ad0e7e1-6085-421b-a179-b0c40de8667c/content
6. Weights and Measures Act 1985, Schedule 1 (definition of the pound: 0.45359237 kg). www.legislation.gov.uk/ukpga/1985/72/schedule/1
7. Royal Society of Chemistry, Periodic Table: Lead (density 11.3 g/cm³). www.rsc.org/periodic-table/element/82/lead
8. GOV.UK, “Report treasure, wreck material or archaeological finds”. www.gov.uk/treasure
9. Treasure Trove Scotland, “Information for finders”. treasuretrovescotland.co.uk/information/information-for-finders/