Shotgun Chokes Which choke should I use? Introduction This article is intended to provide a basic guide for the beginner to clay target shooting and help those people deciding what chokes to buy. Chokes are the subject of many views and opinions among the clay and game shooting world. What is universally important is that good technique and gun fit are far more important to achieving a hit than your choke. Some shooters argue that tight chokes and good technique make a better shot. This is true for practice but when you get into a competition you need every advantage possible so choosing the right choke will maximise your chance of a hit and might just make that bad gun mount or gust of wind into a broken clay instead of a miss. If you have any better knowledge, done any testing and can share it then please let me know and I will incorporate it into this document. What is Choke? Choke is a narrowing of the diameter of the internal bore of the barrel at or near the muzzle. The effect of choke is to create a tighter pattern (or less spread of shot) at the target. Designs of choke have changed over the last hundred years but the basics of length, restriction and shape have not significantly changed. The documented history of its invention is sketchy but W.W Greener developed the first effective method of producing a choked barrel in the 1870 s and did a huge amount of research to develop the most effective shape. Before then all commercial gun barrels were cylinders. Choke was developed at around the same time that shotguns changed to centre pin, breach loading and nitro propellants were beginning to be introduced. Trap shooting was a game involving specially bred pigeons which were released from cages by pulling a string. (The escaped pigeons became town feral pigeons.) Very tight patterns were desirable to get quick kills before the pigeons escaped the game area. How does Choke Work? This is a subject that has never been scientifically proven or demonstrated. There are various mechanisms at play: 1. Shot is squeezed together. 2. Shot is accelerated. 3. Wad and muzzle blast is retarded slightly, blowing shot apart less after muzzle. 4. Shot in a narrower pattern keeps together by slip streaming. The image below shows a side view of shot leaving a shotgun using different chokes:
Note that tighter choke does not give a longer shot stream, it is just narrower. Generally the more choke is used the tighter the cloud of pellets will be. More choke also causes a slightly higher velocity. Pattern is the position of each pellet at a given range when fired against a flat surface. This consists of the spread of shot and the density of shot over the area. The ideal for clay target shooting is an even density across the whole surface of the area. Unfortunately this is impossible to produce but manufacturers continue to try to convince us that their latest products get nearer. In reality a pattern is measured by the percentage of shot which falls within a given diameter at a given distance, i.e. the effective shot. The shot which falls outside is too spread out to provide a useful chance of causing a break. See the image below for an example of how a cylinder (no choke) and full choke affect the pattern.
Other Factors to Consider Wad: A plastic wad cups the whole shot load along the whole length of the barrel, it keeps it from direct contact with the barrel, lubricates it and forms a better gas seal than fibre. Logically a plastic wad should therefore tighten a pattern. In modern cartridges the effect is not measureable and fibre will pattern the same as plastic. In the early 1900 s and even as late as the 1960 s special wads were available which affected pattern, usually spreading the shot more. My dad tells me that they used to use square shot on the centre stand of skeet to create a wide cloud at very short range. Barrel Length: This is another subject of great debate among shooters. The amount of explosive and speed of burn of a cartridge can have a dramatic effect on pattern due to muzzle blast. A longer gun accelerates the shot for longer and the barrel pressure is lower when the shot leaves the barrel. This means that the shot moves away from the muzzle further before the lower pressure muzzle blast blows it apart. In a shorter gun the shot is closer to the muzzle and subjected to a higher pressure blast. (This is also why a shorter gun sounds louder.) Cartridge Speed: Faster is not necessarily better, but this depends on the propellant. A cheap faster cartridge will tend to have more propellant and a greater pressure at the muzzle, causing muzzle blast to spread the shot and make a lot of noise. A cartridge can be fast and have lower blast by using a faster burning propellant which delivers the energy to the shot early in its travel up the barrel and having a lower terminal pressure. The Weather: Yes, the weather will change the way your propellant burns, the speed, the pressure and ultimately the pattern. Damp propellant burns more slowly. Age: Your gun will slowly wear out and the barrels pitted and perhaps scored. The same happens at the choke and will affect pattern. Steel shot may accelerate this. Which Multi-Choke System is Best? I suspect that manufactures continue to introduce new choke designs to ensure that there is a constant demand for new expensive chokes, rather than improved performance. In my experience a shorter lighter choke is lighter, needs a less bulky choke sleeve and results in a better balanced gun. The trend is currently to longer and extended chokes. W. Greener determined that a choke over two inches in length adds no discernible advantage to pattern. Which choke should I Use? This is the main question people ask, and everyone else will give a different answer. Every gun is different, every cartridge brand is different and every cartridge is different. Even the weather and humidity can affect the propellant burn and change the velocity and therefore the resultant pattern. The only real way to know is by firing your gun at a paper target and having a look at the patterns with different chokes. What a clay shooter needs is a pattern dense enough to guarantee a target break at a given distance. i.e. No gaps in the pattern that are larger than the aspect of the clay target
in the central area of the pattern. Remember that the pattern is always densest at the centre. My advice for clay shooting is to under choke rather than over. For wing shooting a clean kill is needed so more choke will put more pellets into the right place so use at least ¼ more than shown in the table below. The following table is for guidance only for use with edge on crossing targets. A full face target will needs around 3 chokes less. Manufacturer marks do vary across brands and years. The only way to check a choke reliably is to use a gauge. Choke (US) Choke (UK) Optimum Range Notches Barrel Markings (yards) Cylinder Cylinder <20 IIIII ***** Skeet Skeet 22.5 IIIII **S or S Improved Cylinder 1/4 25 IIII **** Light Modified 3/8 30 Modified 1/2 32.5 III *** Improved Modified 3/4 35 II ** Light Full 7/8 35 Full Full >40 I * Extra Full >40 I Choke tables usually include measurements. I have not included these because barrel diameters vary. For example Browning back bored barrels are slightly larger. I do not recommend using a cylinder choke. A skeet choke is a better alternative because it provides a very small amount of effect and will reduce the number of outlying random pellets. This is probably due to was retardation reducing muzzle blast. Full choke is the most choke which a barrel can effectively have. If more choke is applied then the pattern is not reduced or improved more. The pattern may be made worse by the added deformity caused by the squeezing of the shot together further. In the US extra full and turkey chokes are popular but these are only of any use for very large shot sizes which are illegal in the UK without a firearms license. How to Identify a Choke It is very important that the correct type of choke is used in the correct gun. i.e. DO NOT use an invector plus choke in an invector barrel, even if it appears to fit. If you do not know what choke to buy the best way is to remove one and compare it to the one you are thinking of buying. Most chokes state on them what type they are and what amount of choke they have. If not then they may have notches, refer to the table above or the following photo. Cheaper brands of gun can be difficult to obtain replacement chokes for, look after the set supplied with the gun. If buying a second hand gun make sure chokes are available. For a fixed choke gun look firstly at the barrel markings and refer to the table above. On some guns the forend needs to be removed to access the markings.
The star and notch system is designed so that markings can be added when the choke of a gun is reduced. (If this is done then the gun will probably have to be re-proofed and the proof house may add choke markings.) Extended Choke? I have seen no evidence that extended chokes perform any better or any worse than flush chokes. They do allow the user to read what choke is inserted more easily than looking down a barrel (not recommended). They also provide a sacrificial piece of metal which could take a knock rather than your barrel. They make your gun look more blingy, which is good or bad depending on your point of view. They make your barrel slightly longer for less weight. A longer barrel also produces a slightly higher velocity and slightly less muzzle blast. Ported Choke? There are three common claims made about ported chokes: 1) Improved pattern caused by wad retention. The ports allow some gas to escape sideways and slow the wad as it leaves the barrel. This has some merit, but the porting would need to be far enough up the barrel to vent gas before the lead reaches the muzzle. Most ported chokes have the ports a few millimetres from the muzzle. Effective Muzzle brakes. 2) Reduced recoil. Recoil can be reduced using a large muzzle brake, the ejected gases push against the brake and consequently push the barrel forward. This is used effectively on many large calibre guns and tank cannons. The face area of metal presented in a shotgun choke is insignificant in comparison and likely has an insignificant effect. Note that a brake on a rifle is for a different purpose, it slows the muzzel blast in a controlled manner to maintain stability of the bullet. This is what an effective muzzel brake looks like:
3) Less muzzle jump. This is complete rubbish. Muzzle jump can be reduced by porting the top of barrel, but it must be done far enough from the muzzle that enough high pressure gas pushes the barrel down (about 3-4 inches from the muzzle on a shotgun). Ports are mainly used in hand guns and can be effective. A ported shotgun choke is used at the end of the barrel and therefore has an insignificant amount of time for the high pressure gas to have any effect. The ports are also in all directions so the barrel is pushed equally in all directions, negating any effect! Ported chokes are nothing more than a marketing gimmick. They increase noise behind the gun and cause more smoke to come back at the shooter. Can I Use my Gun Without a Choke Tube Fitted? If your gun uses multichokes then NO. The section of barrel where the choke is fitted is thinner and must have a choke installed to take the pressure. Failure to use a choke tube could cause a barrel split, cause expansion of the barrel and will cause damage to the threads. A gun damaged in this way is out of proof and is illegal to sell. Conclusion Pattern your gun. If the pattern is bad switch cartridge before spending money on fancy chokes. At the shooting ground choose your chokes wisely before you start and do not start changing them to try and get hits. You will do more good worrying about your stance, mount and technique. For sporting clay shooting ¼ and ½ choke should suit most scenarios up to the range of your gun. The one exception to this is the mini clay at range. It has a much lower surface area and will need a much tighter pattern. Step up to a 3/4. For skeet stick with skeet chokes. I only use tighter when practicing. For game shooting it will depend on the quarry and height of the birds but generally no less than half for high birds. I am not going to comment on trap shooting because every shooter has their own preference.