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Shotgun Basics

Updated: Feb 28, 2023

A shotgun is a very simple device in principle. You need a tube, sometimes two. The tube(s) are sealed shut at the back except for a hole through which a tiny hammer can strike the back of a cartridge. You then need a means of making that hammer fall on command, and something to hold onto. The tubes are the barrels; the mechanism which makes the hammers (or strikers) work is the action or lock; you hold onto the stock. Thus you have lock, stock and barrel.


In the UK, most of the shotguns used for clay shooting have two barrels, one on top of the other. We call this an “over and under” shotgun, abbreviated to O/U. For most people, an over and under is easier and more comfortable to shoot than a “side-by-side” (SxS) which has the barrels horizontally next to each other. Side-by-sides are the traditionalist's choice for game shooting. They tend to be significantly lighter than O/Us which is handy when you're carrying a gun all day. Unfortunately, recoil is inversely proportional to the weight of the gun, so an O/U makes more sense for a gun which is carried a little and shot a lot. Most side-by-sides also have double triggers - one for each barrel. It's a significant handicap in clay shooting to have to move your shooting hand between shots to use a different trigger. Most O/Us have single triggers with a barrel selector (usually combined with the safety but sometimes a switch in front of the trigger) so you choose which barrel fires first. Usually you fire the bottom barrel first as its lower axis makes for less "muzzle flip" on firing.


12g O/U (top) and 20g O/U


Regardless of barrel orientation, on a double-barrel gun pushing a lever allows the barrels to pivot down from the action so cartridges can be loaded and unloaded. This open position is how the gun should be held at all times until it’s put into a rack or a gun slip (a soft case), or until you’re in a shooting stand, facing in a safe direction and ready to shoot. If the gun has ejectors (and most do), these operate when the gun is opened to throw fired cartridges clear of the gun – you learn to catch them pretty quickly as it saves you from having to pick them up by hand!



Above the top barrel of an O/U or between the barrels of a SxS, there is a strip of metal called the rib. This leads your eye towards the target. Some people will tell you never to look at the rib; youmay hear "stare the target to death" or something similar. In reality, you’re very unlikely NOT to notice a 80cm long, metal thing right underneath your eye! At the front of the rib there’s a bead, and some guns have a smaller bead half way along the rib as well.



A shotgun’s barrels are smoothbore – they have a smooth internal surface. A rifled barrel, in contrast, has helical grooves cut or formed into the internal surface, or bore. Those grooves impart spin to a bullet – this is the single projectile which is part of a rifle cartridge. A shotgun launches multiple projectiles – 350 or more in a typical clay shooting cartridge. These projectiles are called shot, hence the name “shotgun”, and are spherical pellets usually made of lead. Other metals are increasingly being offered as alternatives to lead due its toxicity. The cost and effectiveness of these alternatives are constantly improving.


The shotgun cartridge is where chemistry results in physics. At the back of the cartridge – known as the head – there is a small, metallic cup which contains a tiny amount of an explosive compound. This cup is called the primer, and when the striker hits it the compound inside ignites and makes a spark which lights the gunpowder inside the cartridge. The result of this ignition is gas, rapidly trying to expand and creating a great deal of pressure. Sitting between the powder and the shot, forming a gas seal and preventing the shot from being melted into a single blob, is the wad. This can be paper, fibre or plastic (sometimes biodegradable plastic), and as the gas pressure builds behind it, it pushes the shot along the barrel.


Over the last few centimetres of the barrel’s length, its internal diameter reduces slightly (the maximum reduction is about 40 thousandths of an inch, or 1mm), and this constriction is called choke. Choke is used to control the extent to which the shot spreads out as it leave the barrel. Most guns used in clay shooting now have a removable portion of barrel called a choke tube, so you can choose how much choke you want. Assuming you put a different choke in each barrel, the barrel selector allows you choose which choke to use on which target of a pair. We have an article all about choke if you'd like more information.



Most of your contact with the gun when shooting is with the stock, usually made from a piece of walnut root. This, and any engraving on the action, is the gunmaker’s chance to show off. High grade stocks can be very beautiful and very expensive, though they do nothing to help you point the gun in the right direction. As well as your hands and shoulder, the stock makes contact with your face. Consistent contact here is a vital part of shooting as it determines the relationship between your eye and the rib. A very useful feature for a newcomer to clay shooting is a stock with an adjustable comb. This makes it much easier to make the gun fit you, and thus to ensure that the gun points where you intend.


An alternative to an O/U is a semi-automatic shotgun, though it’s perhaps best avoided as a first gun as there's extra complication involved in proving them safe. They have single, fixed barrels (in some cases the barrel moves by a centimetre or so on firing, but remains aligned with the action) so you can’t prove so easily that they’re empty and open. Underneath the barrel is a magazine tube; with a UK Shotgun Certificate you cannot buy a gun with a magazine capacity greater than two cartridges, and whilst it is physically possible to use it as a three-shot gun (one in the barrel, two in the magazine), CPSA rules do not allow more than two shots at a registered shooting ground. The benefits of a semi-automatic can be lower recoil and the fact that they are usually fairly inexpensive. If you do choose a semi-automatic gun, it’s a very good idea to buy a breech flag for it – this is a brightly-coloured plug with a streamer attached, and it fits into the breech end of the barrel to demonstrate that there isn’t a live cartridge there.


Shotguns come in a variety of calibres, or bores, to suit different people and different purposes. “Bore” can mean, as mentioned above, the internal surface of the barrel, and it can also mean a measurement of its internal diameter. For the latter definition, “gauge” is used interchangeably with bore. A 12 bore/12 gauge gun is so called because a lead ball which perfectly fits the barrel would weight 1/12th of a pound. For a 20 bore, it would be a lead ball weighing 1/20th of a pound. Because the barrels of a 20 bore are smaller in diameter, they are lighter than those of a 12 bore. The action of the gun is usually commensurately smaller and lighter too, so it’s generally easier for a beginner to handle a 20 bore gun. The downside of a lighter gun is that for a given amount of shot it tends to recoil more than a heavier gun.




With modern cartridges, the good news is that fairly light shot loads can be highly effective even on fairly tough, long range targets. Most shooting grounds sell cartridges which are designed to perform well with little recoil. Olympic shooters and others at the top end of the sport, both women and men, often shoot over 500 shots a day, several days a week in training. They wouldn’t do that if it hurt!

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