Air rifle and air pistol pellets: 4.5 or 5.5 mm, and which shape

• For ISSF 10 m air rifle and air pistol you need 4.5 mm pellets, and the ones made for paper have a flat head: wadcutters.
• Match pellets come in rifle and pistol weights and several head sizes. Only a test shows which suits your gun.
• Test from a rest, one card per group, and compare the size of the groups, not the scores.
• Keep pellets dry in a closed tin, and dented ones out of anything that counts.

When groups open up with a pellet you trusted, check the pellet first: pellets damaged in the tin or in a pocket, a new batch, or a new head size. Then the gun and yourself; for yourself, see Reading your shot groups.

Pellets are sold by calibre, in millimetres or in inches: 4.5 mm is .177 and 5.5 mm is .22 (H&N lists its .22 pellets at 5.51–5.52 mm). The barrel decides which one your gun shoots, so the calibre on the tin must match the one on the gun. For ISSF 10 m air rifle and air pistol the rules are short:

10 m air rifle

Calibre 4.5 mm (.177 in). Projectiles of any shape made of lead or other soft material are permitted.ISSF Rifle Rules 7.4.6, ISSF Rule Book, Edition 2025 (Second Print 07/2026), effective 1 July 2026

10 m air pistol

Calibre 4.5 mm (.177 in). All projectiles used must be made only of lead or similar soft material. Jacketed projectiles are not permitted.ISSF Pistol Rules 8.4.4, ISSF Rule Book, Edition 2025 (Second Print 07/2026), effective 1 July 2026

Outside the rule, the difference is in how the pellet flies. Air Arms, a British rifle maker, describes .177 as the calibre with the higher velocity and flatter trajectory, preferred for precision target shooting, and .22 as slower, with a more pronounced arc. The bigger pellet is also heavier: in RWS’s Meisterkugeln range, the 5.5 mm pellet weighs 0.91 g against 0.53 g for the 4.5 mm rifle pellet, about 1.7 times as much.

Other calibres exist too: JSB makes .20, .25, .30 and .35 long-range and hunting pellets, none of them allowed in ISSF 10 m air rifle or air pistol. The card you shoot there, and how it is scored, are on the ISSF 10 m air rifle target page.

A pellet has a head in front and a thin, hollow skirt behind; together they seal the barrel. The heads differ, and RWS and Air Arms name the same four basic shapes:

The ISSF air rifle rule allows any shape, but match pellets are wadcutters. JSB writes that the flat head of its match pellets gives ideally round and sharp hits in paper targets, and RWS that the flat nose gives sharply punched shot holes.

If you also shoot at longer distances, on a range that allows it, try a domed pellet there: RWS credits the round nose with improved aerodynamics, especially for accurate shots at longer distances.

A 4.5 mm match pellet is not always 4.50 mm across the head. Makers sell one pellet in several head sizes, a hundredth of a millimetre apart:

Air Arms explains why: head size affects how tightly the pellet fits in the barrel. Too loose and you lose pressure, too tight and the friction increases. JSB makes its match pellets in a wide range of weights and diameters so that one can be chosen for each rifle, and H&N notes that each air rifle has a slightly different barrel and pressure build-up.

You cannot see from the outside which size your barrel likes. Take two or three neighbouring sizes of the same pellet and test them against each other. JSB sells test kits: its Match Diabolo Test Middle Weight holds 50 pellets each of seven variants, two match pellets in three head sizes each and one more.

Match pellets come in several weights. RWS sells its Meisterkugeln at 0.53 g for air rifles and 0.45 g for air pistols. JSB makes its lightest match pellets, 0.475 and 0.500 g, for the pistol, for a higher muzzle velocity, while its 0.535 g pellet suits both rifles and pistols. H&N’s Finale Match comes as Light, 7.87 gr, and Heavy, 8.18 gr. A grain is about 0.065 g, so those are about 0.51 and 0.53 g.

Pellets well above match weight are made for distance and power: H&N’s long-range Baracuda Match weighs 10.65 gr, about 0.69 g, and H&N asks for a minimum muzzle energy more than twice that of its Finale Match. So a pellet that heavy is not a better 10 m pellet; it is made for a more powerful rifle. Start with the weight made for your gun: rifle weight for a rifle, pistol weight for a pistol.

Lead-free match pellets, made of tin alloys, are much lighter: RWS’s HyperMatch weighs 0.33 g and H&N’s Match Green 5.25 gr, about 0.34 g, which H&N says is only for PCP rifles. Air Arms notes that lead-free pellets sometimes give less consistent results in certain rifles, so test them like any other.

A pellet test compares pellets, so take as much of yourself out of it as you can. H&N recommends a test with the barrel held fixed at a range, done by a specialist; a sandbag gets you close enough to tell the best pellet from the worst.

1. Pick three or four candidates: two or three head sizes of one pellet, and the pellet you shoot now.
2. Rest the gun on a sandbag at your usual distance, on a range or, where the law lets you, into a pellet trap rated for your gun, indoors or in still air, in the same position for every pellet. A pistol goes on the bag by its cylinder or frame, with your hand on the grip as you shoot; or rest your wrists on the bag and hold the pistol as usual.
3. Give every group its own card, and write on it the make, the weight, the head size and anything printed on the tin that identifies the batch.
4. Before a new pellet’s group counts, fire two or three of them off the card. If you have just cleaned the barrel, shoot a few more first.
5. Shoot at least five groups of five with each pellet.
6. Take the pellets in turn, a group of each and round again, so tiredness and light fall on all of them alike.
7. Test the best two again on another day before you settle on one.

Compare the size of each pellet’s groups, not where they sit on the card. A new pellet can move the point of impact, which your sights can fix; they cannot make a wide group small. Watch for fliers too: a shot well away from the rest, again and again, can mean damaged pellets or a poor fit.

The makers’ own figures come from their own tests, not from a shooter. H&N writes that from a fixed barrel, a series that matches the rifle can leave a single hole of just 5 mm across after 10 shots at 10 m. JSB requires its match pellets, shot in groups of five at 10 m, to show what it calls an average central scatter of up to 1.5 mm, with a circumscribed circle of up to 6 mm. Your groups from a sandbag include you and will usually be larger; what matters is which pellet groups smallest.

This is where Shooter helps. Log each pellet as its own session, with the pellet in the notes, and photograph each card: the app scores it and gives the group size. A full test takes more scans than the free ones; after them, Pro scans without limits on cards the phone scores, and other cards use AI credits or hits you mark yourself.

When you open a new batch of your pellet, shoot a group of it beside the old one before a competition. What a group’s shape says about you rather than the pellet is in Reading your shot groups.

A pellet groups well only while it is undamaged. Air Arms lists what spoils them: pellets can deform inside the tin, and transport or rough handling can change their shape. Even slight damage to the skirt or head affects how they seal in the barrel. Moisture can oxidise lead, and dirty pellets add friction.

• Keep pellets dry, in their tin with the lid on; Air Arms recommends sealed containers.
• Carry the pellets for a session in a small box or a pellet tray, never loose in a pocket or a bag.
• Pick a pellet up by the head and load it without squeezing the skirt.
• A pellet that fell on the floor or has a dented skirt goes in the practice tin, not in a match.
• Do not mix head sizes or batches in one tin, and label anything you decant.
• Most pellets are lead: never hold them in your mouth, keep tins away from children, and wash your hands with soap after a session and before you eat.

Is .177 the same as 4.5 mm?

Yes. .177 is the calibre in inches and 4.5 mm in millimetres, and the ISSF rule writes both. For air pellets, .22 is 5.5 mm, while the same ISSF rule gives .22 rimfire as 5.6 mm.

Which head size should I buy for my gun?

Only a test tells. Take two or three neighbouring sizes of the same pellet, such as 4.49 and 4.50 mm, shoot them from a rest, and keep the one that groups smallest.

Do heavier pellets group better?

Not by themselves. Rifle match pellets weigh around 0.53 g and pistol match pellets 0.45–0.50 g; pellets well above that weight are made for longer distances and more powerful rifles. Your barrel decides, so test.