Understanding Choke Tubes
Shotgun chokes might be one the most misunderstood things in the gun industry. While in principle most people understand that a choke affects shot pattern, few people really grasp the total number of variables involved, or the most effective way to utilize their choke. There is fortunately a vast amount of good, and even great information out there. But as with most things, sorting through the good, the bad, and the worthless can be time consuming and frustrating. What I hope to accomplish with this article is to guide you through some of the information available, and to help empower you to get the absolute most out of your shotgun and your choke(s).
While the word "Choke" has multiple uses and definitions, the one that pertains to shotguns is as follows from the Merriam-Webster Dictionary: "to obstruct by filling up or clogging". So what exactly is a choke on a shotgun? In its most basic sense, it is the amount of restriction in the bore of the firearm. What is the purpose of the choke? To provide a better shot pattern for a given application. Some of you might be wondering "So, what does this mean to me?". Well, this is where it gets slightly more complicated. Lets start at the very beginning and work our way through it.
First of all, let's clear up how people define the different levels of choke available, and what that means. There are many variables to the information I am about to give, and if you look for your own information you will likely find some different answers. The information below comes from the "Complete Book of Rifles and Shotguns" by Jack O'onnor. While this book is old (copyrighted in 1961), the information has not changed much, and is often found referenced by other knowledgable sources as being relevant to this day. The way shotgun choke is measured: The percentage of pellets that hit inside a 30 inch circle at 40 yards. The values given by O'Connor are as follows (Full Choke below is the most restrictive, Skeet #1 would be least):
- Full Choke: 70-80%
- Improved Modified: 65-70%
- Modified: 55-65%
- Quarter Choke: 50-55%
- Improved Cylinder: 45-50%
- Skeet #2: Usually delivers a "Modified" pattern
- Skeet #1: 35-40%
As you read from the above information, as the restriction of the bore increases, the shot spread decreases or narrows. Another batch of information provided by O'Connor would be the following table:
Spread of Shot Pattern in Inches at various yards:
Again, the data indicates that as the restriction increases, the shot pattern decreases, or narrows.
So now that you know how shotgun patterns are measured, how do you pick the right one? According to Elmer Keith in his book "Shotguns by Keith" (another classic, this one from 1967), "The degree of choke, however, must be governed by the ranges at which you must take your birds or fowl. What you want is as near an even 30 inch spread of pattern at the range at which you kill your game as possible. This will give you some leeway in accurate gun pointing and the aim can be off the mark a few inches on either side or high or low a few inches and still kill, providing the bird is well within that 30 inch circle." Elmer Keith hits on something very important in this quote. While shotgun chokes are categorized by how they perform at 40 yards, most game is harvested at much shorter range. You must try to keep in mind at what distance you usually hunt when considering a choke. The closer you are, the more open the choke needs to be.
Far be it from me to change something Elmer Keith said, but I would like to add: you must also consider the ammunition you are using as well. Is it high velocity? Is it #8, #6, #4? Are you shooting a turkey load? Are you shooting lead or steel? These are all considerations when determining which choke to use, to achieve the optimal 30 inch coverage. Also remember that no two guns are identical. They are all a little bit different, and that can change the interaction between the shotgun, ammunition, and choke. While it may seem that there are too many variables to be confident in selecting a style of choke, that is not necessarily the case. What is important is to get as close as possible to what you need, and then later pattern the shotgun so you know how your combination is reacting. According to the chart above, if your hunting range was consistently 35 yards you should be looking for a "Full" choke, as it purports an expected shot pattern of 32 inches. If the yardage was closer to 30, then you would be looking for a "Modified" choke, with again a 32 inch pattern. Closer yet, say, 25 yards? "Improved Cylinder" would be what you are looking for.
Now that we have gone over what the different styles of choke do, and what it is we are looking for in a choke to suit our needs, we need to verify that the choke is performing as expected. It is absolutely key to pattern your shotgun with the new choke, the different loads you expect shoot from it, and do it at several different distances. In fact, when looking at the box of Winchester Super X #4 shells next to me, it says to pattern your shotgun at 20, 30, and 40 yards. Now 20, 30, and 40 yards are simply recommendations, and you could certainly choose to do something different. However I would recommend sticking with something simple like 20, 30, and 40. Ultimately, it is up to you and how you are most likely to use the shotgun. The reasoning behind this is all the things I mentioned a couple of paragraphs back: it is impossible to know exactly how your gun, that particular ammo, and the choke will interact, until you actually fire it. Patterning a shotgun is not a short and easy task. It is actually fairly arduous and a lot of work, but you will be better for it.
I have heard recommendations of as little as two shots per distance, per load; and up to 10 shots per distance, per load. This is ultimately a decision up to you, the user. All I would remind you of is, that the more you pattern per distance, per load, the more accurate your understanding of the overall pattern will be. In order to pattern a shotgun you need to know how many shots per distance, per load you are firing; the number of loads you want to pattern, and the distances you will pattern at. For example, if I were to pattern Winchester Super X #8, and Winchester Super X #6 at 20, 30, and 40 yards a total of five times per distance, per load, I would be firing a shotgun a total of 30 shots! Five shots of #8 at 20 yards, five shots at 30 yards etc, and then repeat with #6. Remember that you will need a target for each shot! I would also remind you that results may differ between brands, so I would recommend patterning with the ammunition you plan on hunting with for the most accurate results.
Generally what I have seen recommended and what I used recently for a target is a 48 inch by 48 inch sheet of paper. It is beneficial to have a mark roughly six inches round in the middle to aim at. It doesn't need to huge or elaborate, just large enough to aim at from the furthest distance you are going to pattern from. It should also be labeled with load, distance etc. You then systematically go through making all your shots. After shooting, find somewhere comfortable to sort through the data. You are looking for the highest concentration of pellet holes on the target sheet. Not necessarily where you were aiming, but, the highest density of shots on the paper. Once you determine where the "center" of the shot is, you need to make a 30 inch circle surrounding it, and count each hit in the circle. There are several websites that list the number of pellets of a given size and material, or you could even break open a shot shell and count, but in reality, on most shells that would be very tedious and a giant waste of time. In order to know the percentage of shot in that 30 inch circle, divide the number of holes in the target by the number of pellets that are supposed to be in a cartridge. Hypothetically, if you count 70 individual holes in the 30 inch circle, and there were 100 pieces of shot in the shell, you have a 70% hit ratio. You will also need to average the percentages based on shot and load type. This means that if you made that same shot, with the same load, at the same distance five times, you need to find the average of those five shots. So if your results were 70%, 62%, 66%, 73%, and 67%, you would add those results together and divide by five. If you were testing this choke and load at 40 yards, it would be considered an "Improved Modified" choke as it returned a 67% average hit ratio. If you want to have a particularly detailed understanding of your choke, you can take your 30 inch circle and divide it into four quadrants. When you compare the results of those four quadrants with one another, you may find that the choke/shotgun/shell combo patterns heavy left, right, up, down, or any other combination there of. Typically you would want it as even between the four as possible but this could be valuable information if your setup tends to favor a direction. Ultimately if you are not happy with the results, don't be scared to experiment. Try a different choke/choke setting (depending on if it is a fixed or variable choke), pellet size, or style of ammo to be more in line with what you require.
Example of a home made target.
Example of a short range shot pattern on target (Please note that this pattern is under 30 inches, and as such no circle was drawn on this target, but it still contains valuable information. We could measure shot spread from a known distance, and what kind of overall pattern the choke is producing.)
So in a quick recap, why do we pattern shotguns? Because it helps us become more proficient with our firearm, by increasing our knowledge of its specific capabilities in given situations. Let us also review the steps to patterning a shotgun:
- Plan! What distances are you patterning, which types of ammo, how many total shots, how many targets, what order are you going to shoot etc.
- Gather Supplies! Make/purchase the targets, organize equipment etc.
- Go Shooting! Follow the plan, make sure that targets are labeled so the data is as useful as possible.
- Evaluate the Data! What was the shot spread at 10 yards or 20 yards? Did brand "x" pattern better than brand "y"?
- Integrate! Incorporate the information you gained into making better shots, changing chokes, changing hunting distance etc.
If you take any one thing away from this article, I hope that you take the time to become more familiar with your firearm. I have heard that not patterning your shotgun is the same as putting a scope on a rifle and never sighting it in. While that may seem like a drastic comparison, it is a very applicable analogy. If you haven't patterned your shotgun, how do you know what it will do? If you take two things away from this, I hope you have a new appreciation for the interaction between a shotgun, choke, and ammunition. Depending on velocity, weight, bore diameter etc, there can be a lot of variation in how it all interacts, and what kind of pattern it produces. More than anything, what I hope is that you go out and utilize the investment you made in your shotgun and chokes to get better results in the field!
This review written by Joel Zielke an independent product reviewer.