Choke and choke selection is the topic that baffles newcomers to clay shooting more than any other. Mix arcane terminology with some fuzzy science and a healthy dose of prejudice and you have a recipe for total confusion. Baffling marketing claims and seemingly conflicting advice depending on who is giving it just make it worse. Can we shed some light on the subject?
What does it do?
Choke is a constriction of the bore at or close to the muzzle, designed to modify the shot pattern after it leaves the barrel. Soon after it leaves the barrel it meets wind resistance and the tight column of shot begins to spread out to form an elongated cloud. The width of this cloud is called the spread and its length from front to back is called the shot string.
Try shooting a relatively small and fast moving target with a single lump of shot (ie a bullet) and the chances are you will miss. Sporting shotguns were designed to kill game at a range of 15-50 yards. By breaking the lump of lead into lots of smaller pieces (the shot) the shooter reduces the need for pinpoint (and near impossible) accuracy. With a shot pattern of about 30” (76 cm), near enough is usually good enough to achieve a kill, relying on the impact of multiple strikes.
The way the pattern develops is dependent on several factors, including the hardness of the shot and the speed at which it is travelling. Softer shot deforms more as it passes through the barrel and is less stable aerodynamically. Deformed shot will tend to veer away from the main pattern very quickly and higher velocity can produce the same result. The greater the distance travelled the more the pattern opens out until the pellets are so scattered that it is completely ineffective.
In the late 19th century it was discovered that if you constrict the bore at the muzzle by a relatively small amount the pattern spread can be controlled and the effective range of the pattern extended. ‘Choke boring’ was soon all the rage and has been a feature of shotgun design ever since. Full choke in most guns represents a constriction of around 40 thousandths of an inch but this small change has a dramatic effect on the pattern. Using the data from that perennial favourite, the Eley Shooter’s Diary, we see that a true cylinder gun (no constriction) will put 70 per cent of the pellets in a 30” circle at 25 yards. With full choke the pattern will still contain 70 per cent of the pellets at 40 yards.
The Holy Grail of shotgun patterns is one that has all the pellets evenly distributed across the magic 30” circle. With such a pattern, no target within the circle would escape unbroken. The reality is that every pattern you see will be denser in the centre than at the edges. Plotted on a graph you would see the classic bell-shaped distribution curve. It means you have overkill in the middle – that is you are likely to get far more pellet strikes than you need – while at the edges pattern density may be getting marginal. There are ballistics experts who would argue that relying on the fringes of the pattern too often will inevitably lead to lost targets and that the true effective spread for complete certainty is nearer to 20” than 30”.
Many shooters, including some of the world’s greatest, shoot fixed choke guns. Some prefer the handling characteristics, believing that their gun has better weight distribution without added weight at the end of the barrel. This can be a factor and can influence your choice of interchangeable chokes. Others prefer to exclude choke as a variable, believing that the time spent considering choke choice and making changes is better spent studying the target.
It is fair to say that the majority of those who elect for fixed choke guns shoot with barrels that are tightly choked. In effect they are setting up with the best combination for the hardest targets and accepting a less than optimum choice for closer range work. As highly skilled shooters they are prepared to accept a slightly smaller margin of error on targets they would expect to break 99 per cent of the time.
Others will make a choke selection for each stand on a Sporting course – all very well, but which choke is the right one for any given target? Once again there is no hard and fast rule, but if you understand distance and target presentation it can be an informed judgement.
Let’s take distance first: Skeet shooters take all their targets within a 25 yard range. They quickly worked out that the best results are obtained by shooting very open chokes to give the pattern the best chance to open out over relative short distances. Furthermore, as the pellets have retained most of their striking energy at short range, smaller shot can be used to increase the pattern density. The classic Skeet load of number 9 shot through open chokes is perfectly balanced for the job and has been proven literally millions of times.
Trap shooters on the other hand have a different problem. All their targets are flying away from them, so the range increases dramatically every second. They need the energy of several strikes from relatively large shot to break with authority. Moving to larger shot means reduced pattern density; tighter chokes compensate for this density loss. This leads us to the typical tightly choked Trap gun set up. Three-quarter and full or full and full have become the norm over decades of competition.
Distance then is the first thing to consider. ‘Full at 40’ is an old adage that still holds good today. Remember that full choke should deliver a 70 per cent pattern at this range. To maintain that percentage you can, as a rule of thumb, open up one choke for every five yards you are closer to the target.
The other key factor is presentation. As we discussed, edge-on targets are much harder to break. A 35 yard edge-on crosser can be more of a challenge to both shooter and equipment than a 50 yard driven target. The visible area is considerably smaller and the face presented to the shot is the thickest and hardest. A target showing its full belly on the other hand exposes the thinnest part of the clay and will require fewer pellet strikes for a clean break.
Choke selection then is part art, part science and (hopefully) now a little less mystery.
The interchangeable choke has had a profound effect on shotgun design and given the thinking shooter a real advantage.
Early manufacturers’ chokes were, however, often of variable quality, cheaply machined of poor grade steel and distinctly patchy in performance. Given that the choke plays a large part in a gun’s performance it seemed to many a strange oversight – rather like putting remould tyres on a high performance sports car. Aftermarket suppliers in the USA saw the opportunity to sell thousands of gun owners a better mousetrap and soon those products were finding their way across the Atlantic. Clay Shooting tested the first of these, from Rhino, back in 1994 and soon replacement chokes could be seen sprouting from the ends of barrels all over the country, with several brands vying for sales.
A lot has changed since then, not least a dramatic improvement in the quality of most manufacturers’ standard products. The latest Optima chokes from Beretta or Browning’s Midas and Titanium ranges are a world away from earlier products and a match for many of the specialists in terms of lightweight, quality of machining and consistent performance. A strong market still exists though for alternatives to the makers’ own chokes, as serious competitors look for every little edge they can get. The choice is enormous: flush fitting or extended; plain or ported; stainless steel or titanium and now there is a battle between American imports and homemade to add a little extra spice.
Each maker will claim some special secret that makes their chokes better. Some say the design of the internal taper is key, others that the length over which the choke tapers is a vital consideration. Porting is a feature on many types of extended chokes, claimed by many to help reduce muzzle flip and perceived recoil, dismissed by others as a gimmick. Some manufacturers also claim that porting has a ‘wad stripping’ effect, retarding the wad and leaving the shot cloud to carry on unhindered. Note: ported chokes are illegal in most Trap shooting disciplines.
Weight is certainly an important consideration. Adding extra weight to the muzzle alters the balance and weight distribution of the gun. Because it is added to the end of the barrel, relatively small amounts of weight can have a marked effect on handling, increasing the polar moment of inertia for the technical types among you. With some guns a little extra weight can be beneficial, helping to steady the handling on a fast moving gun for example. Some of the aftermarket chokes can be surprisingly heavy, so it is worth trying out different types to see what effect they have. If you are trying to minimise added weight then one of the newer titanium alloy types may be the route to go.
Here is a selection of the main brands available from both major manufacturers and aftermarket suppliers:
Jess Briley was one of the pioneers of screw-in choke technology and the Briley name remains one of the most respected today. Many leading gunmakers have also worked with Briley rather than develop their own choke systems.
Chris Potter Country Sports in Kent is the official UK outlet for Briley products and offers a comprehensive selection of nine constrictions: 01892 522208.
Browning moved interchangeable choke marketing forward on mass market guns with the introduction of their longer ‘Invector Plus’ tubes in the early 1990s, designed to be used in conjunction with their ‘backbored’ barrels.
Gemini offer a range of replacement chokes suitable for Beretta and Benelli shotguns. Its experience of many years as a supplier of the most important arms factories in Italy, allows it to offer a product with optimal characteristics.
With extended portions about twice as long as most other brands, there is no missing the Comp-n-Choke range, with its unique slot-ported braking system. The choke design allows gases to vent through slots, parallel with the muzzles, generating a brake system, which the makers claim reduces recoil and gives quick recovery for the second shot.
There’s no doubting the buzz word in choke technology at the moment – titanium. Krieghoff has developed titanium chokes that are longer than the standard chokes but still 20 per cent lighter and the finger grooves make them easy to remove.
Arguably the brand that started the whole thing off over here and certainly the product that made it cool to have something sticking out of your barrels. The specially angled ports are claimed to reduce muzzle flip by up to 15 per cent and to also have a wad stripping action that they say separates the wad from the shot cloud as it leaves the muzzle, greatly reducing pellet disturbance and reducing the number of ‘flyers’.
America has Jess Briley, Britain has Nigel Teague – the choke guru whose conversions of fixed choke guns propelled many a champion to the top. The range includes all the major competition guns, Bettinsoli and Remington being the latest additions to the list. All are available in a choice of flush fitting, extended and ported extended and feature Nigel Teague’s continuous taper profile.
Georgia based Trulock Chokes is a family business that has rapidly become one of the leading players on the American shotgunning scene and their products are now distributed in the UK by Garlands. Trulock chokes are built for strength and longevity from 17-4 PH grade stainless steel, which has an extremely high resistance to staining and rust. Titanium chokes are the latest thing in the Trulock portfolio, their multicoloured Ti tubes being made from a titanium alloy that they claim is 35 per cent lighter than standard steel.