Author: Spencer Tomb
There is more to choke tubes than simply screwing one in.
Thirty-five years ago fixed choke barrels were the rule and screw-in chokes were a novelty. The reverse is true today. Most shotguns come with screw-in chokes and today’s shotgunners have a tremendous selection of well made, aftermarket, extended, screw-in shotgun chokes from which they can choose.
Shotgun makers in the late 1800’s learned that if they reduced the bore diameter of the distal end of a barrel by .020" or .030" that it kept the shot together, giving a shotgun a longer effective range, and the choke was born. The development of chokes was a very important step in shotgun evolution.
The typical American choke designations of Full, Modified, Improved Cylinder and Skeet are based on the percentage of the shot they put into a 30" circle at 40 yards. These designations later evolved into measured constrictions of the bore by .035" for Full, .020’ for Modified .0010" for Improved Cylinder and .005" for skeet. In other words, if your Browning has an internal barrel diameter of .729", an Improved Cylinder choke should have an internal diameter of .719" or ten thousandths of an inch of constriction.
The first thing that is obvious about the aftermarket, extended choke tubes is that they are usually much longer and are easier to change without a wrench. The increased length is important as it lets the constriction taper over a longer distance. The extra length improves pattern consistency and density.
The internal dimensions of aftermarket choke tubes and even shotgun barrels may vary a few thousandths. Mountie Mizer of Beretta USA Explains it this way, "Beretta chokes and all generic production chokes currently available from major manufacturers’ include a minimum and maximum restriction value. In fact, all barrels (excluding custom built barrels) offer a minimum and maximum bore diameter as well. Typically, choke and barrel diameters will range 2 to 3 thousandths (plus or minus). These variances are typical in any production environment. That is why it is so important to pattern your gun! A light modified choke in one gun might be closer to an improved cylinder in another. One does not know until the gun is put on paper."
Marc Murphy of Michael Murphy & Sons has measured hundreds of choke tubes with a micrometer and has found that about 10% of the factory chokes supplied with shotguns are off more than .002". Marc related that modern Browning factory choke tubes tend to be several thousandths more open and that the after market tubes like those from Briley, Carlson, Hastings and Rhino vary less.
The growth in sporting clays and wild turkey hunting stimulated the evolution of choke tubes. You can find any choke constriction you want and lots of other "gizmos" too like extended, ported and rifled tubes. Today most sporting clays shooters use easily changed, extended choke tubes. Most turkey hunters hunt with special chokes that have been specifically developed for turkey hunting. Waterfowl hunters have also started to use extended chokes that are specifically designed for non-toxic shot.
Not everyone has a micrometer that can measure their barrel and choke tubes. It is a little easier to come up with 40" wide paper, a place to shoot and check their chokes on paper. It is important to do both. There is no substitute for seeing the pattern on paper.
To check the patterns on paper, you will need a wooden frame or a shipping pallet, paper that is 40" wide, a stapler, a marking pen, long and short tape measurers, ear and eye protection and a safe place to shoot. Place the pallet or frame where the shot cannot hurt anything. The usual procedure is to shoot at a 4" circle from 40 yards and draw a 30" circle around the center of the pattern and count pellets to see if the chokes are what they say they are. For example a full choke should put 70% of its pellets in a 30" circle at 40 yards and a modified choke should put 60% of its pellets in the circle and an IC should have 50%.
For practical purposes, you should shoot each of your chokes at the distances that you would consider using them, and you should shoot the same loads that you will be using in competition or in hunting. Different loads may pattern differently and two chokes of the same constriction may produce different patterns as well. Distances should be measured with a tape unless you are certain of your stride length. 20 yards is a good distance to test skeet and cylinder tubes and 30 yards is good to test an improved cylinder choke. You should do four to six patterns for each choke and load.
The size of vital area of the bird or amount of the target face that is in view is important too. It takes a denser pattern from a tighter choke to deliver the pellets that will consistently break a target on edge or bag a wild turkey. With targets, you can use a more open choke if the full dome or belly of a target is in full view. To visualize this, make cut outs of life sized game birds and a standard clay target in full view, or a 4" circle, in partial view, or a 4" ellipse and on edge target, or a 4"x1" rectangle using colored acetate sheets and use them to see the number of hits they would receive in a pattern that has been shot. Conventional wisdom is that it takes a minimum of three pellets to break a clay target and that more than twice that is needed on game.
Shotgun writer Don Zutz devised a way to evaluate patterns without a lot of pellet counting and elegant statistics. He would find what looks like the pattern center and draw 20" and 30" diameter circles around it. He called the center circle the core pattern which should be even and dense with neither gaps nor heavy concentrations of shot. The outer circle is the fringe area and it is this area that will tell you if that choke and load were an efficient combination at that range. If it is the right load and choke there will be few if any spaces where a target or bird could slip through the fringe pattern without three or more hits. Life sized cutouts of birds and targets help see these spaces if they are present.
This demonstration lets you see the relationship between your loads, target distance, choke and how much target is visible. It is an over simplification of what goes on because the shot travels as a cloud of pellets and the target is moving. Never the less, seeing this practical demonstration of pattern density and size, in relation to measured distances, will build confidence in your various chokes.
Shotgunners have to be able to estimate distances and know their ability to shoot at various distances. Thirty-five yards is a key distance for most hunters as that is the point where leads get longer and it is a point where you start needing more choke than improved cylinder. It is important to measure your stride on a football field and learn to estimate distances. A person of average height should be able to adjust their stride to a yard per step with some practice. If your legs are significantly shorter or longer it may take more or less than 10 steps to cover 10 yards.
The goal should be to use the choke and load that performs best at the distance you will be shooting. If you expect to have to shoot longer shots, a modified choke and heavier loads would be a reasonable choice. There is a tradition among waterfowl hunters to use tighter chokes, and some seem to forget that steel and other non-toxic loads naturally pattern tighter than lead. Shooting ducks over decoys in ideal conditions often gives close shots that are best made with more open chokes. Non toxic shot loads pattern tighter than lead shot. With steel shot, a skeet choke will give an improved cylinder pattern and is adequate for shooting over decoys most of the time.
It is important to evaluate your hunting style and the distances you normally shoot and use the choke and load that delivers good patterns, at that distance. To get modified patterns duck hunters should use an improved cylinder choke. I have found that for ducks over decoys for shots generally less than 35 yards and a choke with .008-.012" constriction gives patterns that anchor the ducks.
A number of after market choke tube makers are now making choke tubes that are species specific. Briley’s line of extended hunting chokes are marked QU for quail, DU for ducks and GO for goose. Rhino puts numbers 1, 2 and 3 on their extended waterfowl chokes. Briley’s Duck choke is just a little tighter than an IC choke and gives good, dense, modified patterns with steel shot and Remington’s Hevi-Shot.
All of the choke tube makers have their own system. For example Hastings extended chokes for hunting and sporting clays are numbered from 0 to 12. The number on the choke refers to the amount of constriction in the choke in .004" increments. For example, the Hastings # 0 choke is a cylinder bore choke with no constriction and their #2 coke is .008" and slightly more open than a standard improved cylinder (.010"). The #3 choke has .012" and is intermediate between improved cylinder and light modified.
With the phenomenal growth of wild turkey hunting, all of the choke tube makers have one or more types of tight patterning turkey choke. These extended, tight patterning, extra full chokes can give you an extra 15 yards of killing range over a standard, flush mounted, full choke. This can be important when that gobbler of your dreams hangs up at the edge of your range. The constriction in these chokes varies from about .040" to .060". Carlson makes both ported and non-ported turkey chokes and I have found that the Carlson non-ported .665" will give turkey anchoring patterns with 2 oz. #5 shot out to 45 yards in my Beretta 390.
The best way to evaluate maximum range of a turkey choke is to shoot at anatomically correct turkey targets at known distances. You have reached the shooting range limit when your load and choke combination can no longer deliver a minimum of three or four pellets to the bones of the neck or skull. It is important to shoot at least three replicates when you test your loads and chokes. Shot size, load weight and velocity will affect pattern results as well. For example, a 1 7/8oz. #6 patterns better with my Hastings extended turkey choke .670" in my Browning BPS than # 5 shot and 2oz. loads. It is just as important to check the efficiency of your load and choke combination as it is to check where your gun shoots when you aim it like a rifle.
Aftermarket choke tubes will not make you a better shot, but they will give you more uniform patterns and more distance in the case of turkey hunting. You should check them on paper before you use them in competition or in hunting. You can trust the name brands of choke tubes, but you should verify how they shoot your loads in your shotgun and even find a gunsmith to measure their internal diameter.
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