19-Oct-2026
In short, a 12 bore has a larger barrel diameter and can carry a heavier charge of shot, while a 20 bore is usually a lighter, livelier gun that sends a slightly smaller charge. For most British game shooting, both do the job well. The better question is which one suits you, your shoot and the sort of birds you expect to meet. This guide explains what the numbers mean, where each bore tends to shine, and how to decide without getting lost in the folklore.
What do “12 bore” and “20 bore” actually mean?
The numbers come from an old system of measurement. Bore, or gauge, was originally defined by how many lead balls of the barrel’s diameter it would take to weigh one pound. A 12 bore is the size where twelve such balls make a pound, and a 20 bore is the size where twenty make a pound. That is why a bigger number means a smaller barrel, which catches many newcomers out. “Bore” is the usual word in British shooting, while “gauge” is more common elsewhere, but they describe the same thing.
In practical terms, a 20 bore has a narrower barrel than a 12 bore, and therefore a smaller cartridge. The two are not interchangeable in any way, and you should never put a cartridge of one bore into a gun of another. A 20 bore cartridge is small enough to slip into a 12 bore chamber and lodge dangerously, which is one of the oldest and most important safety warnings in shooting. Always check the markings on the gun and on the box, every time.
The 12 bore is the most popular size in the UK, and the one most people picture when they think of a game gun. The 20 bore has always had a loyal following and has been enjoying something of a revival, which our guide to the 20 bore comeback explores.
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How do they compare in weight and handling?
The most obvious difference is often in the hand. A 20 bore game gun is generally built smaller and lighter than an equivalent 12 bore, because the barrels and action can be slimmer. Many shooters find a 20 bore quicker to mount, easier to carry through a long day of walked-up or rough shooting, and pleasant to swing. Those who shoot all day, or who are smaller in frame, often appreciate that lightness.
That lightness cuts both ways. A very light gun can move more in the hand when it fires, so a light 20 bore is not automatically gentler than a well-balanced 12 bore with a lighter load. Recoil depends on the weight of the gun, the weight of the shot charge, and the speed of the load, plus how well the gun fits you. A heavier gun with a modest cartridge can be more comfortable than a lightweight gun firing something punchier. The honest answer is that you need to handle both.
A 12 bore, by contrast, offers a wider choice. There are more models, more actions and more price points, and that includes plenty of well-made second-hand guns. If you want a gun that will cover pheasant, partridge, pigeon and perhaps the odd clay day, a 12 is the easiest all-rounder to find.
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Is a 20 bore enough for pheasant and partridge?
For well-presented game at normal game-shooting ranges, many experienced guns say yes. A 20 bore with a suitable load kills cleanly in the right hands, and generations of shooters have used one for pheasant, partridge, pigeon and ground game. Because a 20 bore carries a smaller charge, the pattern has fewer pellets in it, so there is slightly less margin for error. That makes shooting discipline and choosing the right bird more important, rather than less.
The 12 bore carries more shot, which many shooters find more forgiving on the odd extra-high or extra-fast bird. That does not make it a better gun for everyone. It simply gives you more in the pattern. A shooter who is consistently accurate will often kill more birds with a 20 bore they like than with a 12 that does not suit them.
Please treat any general statement with a pinch of salt. The right load for a gun depends on the bird, the range, the gun and the shoot, and it is something to settle with the shoot captain, your coach or the cartridge maker. A session at a clay ground with a coach is also the best way to find out how each bore performs for you. For wider help on choosing a load, see our guide to cartridge selection.
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What about cartridges, chambers and non-toxic shot?
The two bores share a lot of ground when it comes to practicalities, but there are points worth checking before you buy.
First, chamber length. Many modern guns of both bores are chambered for the standard 2¾ inch (70mm) cartridge, and some are chambered for longer cases. Always check the proof marks and the chamber marking, and match your cartridge to the gun. Our explainer on chamber lengths covers this in more detail.
Second, availability and cost. The 12 bore is the most widely stocked cartridge in the country, with the greatest range of loads, shot sizes and brands. 20 bore cartridges are widely available too, but the choice is narrower, and it is worth checking what your local dealer or the shoot stocks before you commit. Prices vary between brands and over time, so check current prices rather than relying on general statements.
Third, shot material. Whether you shoot lead or non-toxic, the shoot’s own rules and the cartridge maker’s guidance come first. Different shot materials behave differently and not every gun or choke is suited to every load, which matters just as much in a 20 bore as in a 12. Our guide to alternatives to lead ammunition is a good place to start.
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How do you decide between a 12 bore and a 20 bore?
Start with how and where you shoot. If you do mostly driven days, shoot a range of game and pigeon, and want the widest second-hand choice, a 12 bore is the safe, sensible all-rounder. If you spend your time walking up, rough shooting or covering long distances on foot, or you are building a second gun, a lightweight 20 bore may be exactly what you want. Many people end up owning both.
Fit matters more than bore. A gun that fits well will shoot where you look, whichever size it is, and one that does not will frustrate you in either. Read our guide to shotgun fit and, where you can, try several guns at a gun shop or clay ground. If you have a young or smaller shooter in the family, a lightweight 20 bore can be a good first game gun, though again fit and supervision are the key.
Finally, think about the shoot. Some shoots and hosts have their own views and rules on bore, load, and shot, and it costs nothing to ask. If you are unsure about a gun, take it to a gunsmith before you buy.
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FAQ
Is a 20 bore as good as a 12 bore for game shooting? For many shooters it is. A 20 bore is lighter and handier, and with a suitable load it is widely used on pheasant, partridge and pigeon. A 12 bore carries more shot and has a wider choice of guns and cartridges, so it is the more common all-rounder.
Does a 20 bore kick less than a 12 bore? Not automatically. Recoil depends on the gun’s weight, the load, and how well the gun fits. A light 20 bore can feel lively, and a well-balanced 12 bore with a modest load can feel gentle.
Are bore and gauge the same thing? Yes. Both describe the barrel size using the old system of balls to the pound. “Bore” is the usual British term and “gauge” the usual American one.
Can I use 20 bore cartridges in a 12 bore gun? No. Never put a cartridge of one bore into a gun of another. Always check the markings on the gun and the cartridge box, and ask a gunsmith if you are unsure.
Ready to find your next game gun?
Whether you are leaning towards a classic 12 bore or a lightweight 20, the best way to decide is to compare real guns. Browse the latest shotguns for sale on Rightgun.uk, and if you are changing bore, you can list your old gun for other UK shooters to find. If you are unsure about a particular gun, ask a gunsmith or the maker, and check with your shoot about what it prefers.
Further reading: The 20 bore comeback, Shotgun chamber lengths explained, Shotgun fit and Best 20 bore shotguns by budget
