How to Pattern Your Shotgun (and why your choke may be lying)

[Pew Pew Plates 358]

As featured on njshoot!

 

How to Pattern Your Shotgun (and why your choke may be lying)

 

Patterning should be the first thing you do when you take possession of a new shotgun, however all too often I talk to people who don’t even have a clue what their shotgun has for a choke! Patterning is critical, because while your choke my say “modified” on it, how do you know it delivers “modified” performance as far as pattern density? The only way to find out is the pattern!

 

The first step to patterning is to grab yourself some big paper. 40x40 inch is the recommended, but I grab old drawings from work which are 36x48” and work just fine. A freestanding patterning board is ideal, but even an old pallet propped up with a stick makes a great holder for this size paper, too. The dimension of the paper isn’t terribly critical, however what IS critical is your distance from shotgun to paper. Shotgun patterns widen the further out you go, therefore if your choke should deliver 70% pattern density at 40 yards, it will pattern looser if you throw the board up at say…50 yards. This will skew your results. Get yourself a BIG tape measure and measure out 40 yards. The more exact you can do this the truer your results will be!

 

At the range

 

Now we get to start shooting stuff! Ideally, you will pattern every load you may want to use, out of every shotgun, out of every choke. This can be a daunting task, because if you have 4 chokes and 4 different types of ammunition to pattern, that’s a whopping 16 different combinations to try. I recommend you shoot 3-5 patterns with each combination so you get an accurate representation. So you are looking at 48-80 sheets. This is not a process for the faint of heart. Set up your target at 40 yards and draw a POA (Point of aim) that is in the center of the target and just large enough to aim at. Put your shotgun on a rest (yes, bench resting your shotgun!) and carefully fire ONE round directly at your POA. Now, write something on the top of your target so you know which way is up, and write on the target what shotgun, choke, and load was fired at it before you forget. Repeat as necessary!

 

Understanding the data

 

OK, so now you are home, exhausted, and have a massive pile of huge targets with tons of little holes in them. Now what? Well, now comes the fun part.You need to create a 30” circle around the densest portion of your pattern. NOT around your point of aim, but around what you feel is the center of your pattern. You can do this one of two ways. First way is cut out a 30” circle of cardboard with a hole in the middle. Put it over where you want, mark the center (important) and trace it. The other option is use a 15” string and pencil. Either way, make sure that you mark your center for the next step. Now you quarter your 30” circle. Just draw a horizontal and vertical line to divide it up into 4 sections. Following that, count all the holes in each quarter and white the number down on the paper. It helps to tick off the holes as you go. Now you take those 4 numbers and add them together, and put them with your notes on the side. This is your total pellet count.

 

Now you are ready to finally evaluate your pattern. First and foremost, just looking at it you want to see an even distribution of numbers across the 4 quarters. In a perfect world, you want 4 of the same numbers which would mean you pattern is evenly distributed…perfectly. Also, you want to look at how your pattern is aligned with your POA. For a field gun you want your POA to be the same as your POI (point of impact). Lots of trap shooters like to have a 60/40 pattern for rising shots which would mean that 60 percent of the pattern is in the top 2 quarters and 40 percent is in the bottom two. Evaluate your pattern accordingly. You also want to look for any big gaps in the pattern that would allow a target to fly through. The final step is calculating pattern density. This is how you ascertain what choke your load/choke/ shotgun combo is actually shooting. To determine pattern density you divide the total amount of holes in your 30” circle by the total amount of pellets in the loaded shell Here is a table showing the pellets/oz.

 

Shot#, Pellet Diameter (Inches), Average Pellet Weight (Grains), Approximate # of Pellets per Ounce

12 .05 .18 2385

11 .06 .25 1750

9 .08 .75 585

8 1/2 .085 .88 485

8 .09 1.07 410

7 1/2 .095 1.25 350

6 .11 1.95 225

5 .12 2.58 170

4 .13 3.24 135

2 .15 4.86 90

BB .18 8.75 50

 

And with that, you can then get your percentage and see what choke your gun is actually shooting at. This is all assuming testing at 40 yards.

 

Cylinder %40

Skeet 1 %45

Improved Cylinder %50

Light mod %55

Modified %60

Improved Modified %65

Full %70

Extra Full %73

Turkey %75 plus

 

 

So there you have it!

 

Don't be surprised if your “modified” choke actually shoots like a skeet choke, or even a full choke. Anything is possible! This is why patterning a shotgun is essential. If your modified choke performs like a full choke, you do not need to put a full choke on for those further out shots as you will be over choking your shotgun.

 

Decent pattern. Note the top is marked, and the circle

is centered on the most dense portion of the pattern.

The big black criss-crossed circle was my aiming

point.This pattern shows that the shotgun

patterned slightly low on this particular shot but

has decent distribution.This comes out to 73% which

is extra full performance that shot out of a tube

with "modified" restriction.There are some

undesirable voids.

Here is a pretty lopsided pattern out of my Mossberg 20ga. Notice the very uneven distribution and how

it is somewhat off center.

This is a gorgeous pattern! It is off the POA but this can be due to thing like wind, poor aim, or just poor judgment when making the circle. Note the vey even pattern with no voids. This pattern is 56%, out of a "modified" choke so it actually fell 4% short of what it should pattern at.

You can even go so far as to create a spreadsheet to compare loads. Below is a sample of mine. For the 20GA loads at the bottom you will notice notes such as “Full +1”. This is because that particular shotgun had a c-let adjustable choke and I was experimenting with cranking it tighter than full to see if I could get it to choke down more, because of the previous poor patterns. This is a GREAT example of why to pattern, because after this I would NEVER rely on this shotgun to take long shots.

 

Why patterns matter

 

Finally, a brief note on choke tube selection. I prefer the extended choke tubes, and this is for three reasons. My primary reason is ease of changing. If you ever shoot sporting clays and want to take it seriously, you will most likely find yourself changing chokes every now and then. With an extended tubes, you do not need a wrench because you can just grab it and twist it out since it extends out the muzzle. The second reason is ease of identification. It is easy to lose track of which choke is in your shotgun, and most extended tubes are clearly marked on the extended portion. The third reason is pattern quality. Since the constriction takes place over a longer distance it is less likely to deform your shot and degrade your pattern. Once you have patterened your shotgun and are intimatly familiar with your shotgun, you will find yourself changing your chokes all the time for different shooting distances/styles for maximum advantage. This is when you will really want to have the extended tubes for ease of changing, and while your at it, pick yourself up a nice choke tube case to keep them in.

 

If your pattern is less than perfect

 

Now, what do you do if your results are not acceptable to you? If your patterns have voids or are uneven, it can be a factor of the shotguns barrel, the choke, or the ammunition. To determine which it is, simply utilize process of elimination. Try your choke in another shotgun which has an established performance. If the other shotgun patterns poorly with your choke, then your choke is the issue. If it patterns fine with your choke, go ahead and try your ammo in that shotgun. Again, if that yields poor performance, the ammunition is your problem. If that patterns fine, it is a safe bet that there is something wrong with your barrel that is contributing to poor patterns, such as a poorly done back-boring, the forcing cones are messed up, excessive fouling etc. However if your issue is a point of impact that is very far off of your point of aim, your best fix is to sell the gun. There are a few fixes but all are complex and beyond the ability of a tinkerer. A non ribbed barrel can be bent, but I would leave this to a professional. You can also get Briley to cut you an eccentric choke, which is another expensive proposition and it would have to be carefully indexed every time you put it on. As I said before, your best bet here is to sell the shotgun and obtain something with better performance.

 

Extended choke tubes, tube cases, wrenches, and a refrence chart from the choke manufacturer stating theoretical pattern densities.

 

The ultimate in being prepared is having an over/under style shotgun where you can have two different chokes on the gun at the same time, and being able to select which barrel fires first! This is especially advantous if you are doing doubles at a sporting clay course. For example, say you have a report pair. This means that once you fire your first shot, a second clay is thrown. Lets say you have a pump action 870 and a wide assortment of chokes. The first clay is a crossing shot, very close and right ahead of you. The second clay is thown from 20 yards ahead, and goes away from you. You can only select one choke. Which do you chose? If you chose a cylinder choke you will be best prepared for the first clay, however the second clay will be nearly impossible. If you chose a full choke you will have a very difficult time hitting the first clay, but it lets you reach out to the second clay. A modified choke will make each possible, but both would be moderatly difficult. Having an over/under allows you to put on a cylinder and full choke at the same time, and then you can chose to fire the cylinder choke first. This way, your close shot you pull the trigger and the barrel with the cyl choke lets loose on the first clay, and then you fire the barrel with the full choke at the distant clay. Knowing your shotgun and your chokes is important so that you can get the most from your equiptment.

 

 

 

 

 

Whew! Hope that was somewhat informative! Oh yeah, and I know that the guns laid on the paper dont match the patterns, they are just to keep the paper from rolling back up!

[Parker 213]

Nice write-up.

 

You are correct, most people never extensively pattern their shotguns. That would be akin to never zeroing your sights on a rifle or a pistol. Something unheard of but people do it all the time with their shotgun. With choke tubes today I find more variances than with the older style fixed chokes with their known caveats, so I always approach each as suspicious until I've patterned them.

 

Keep in mind that patterns are also affected by shot hardness (the harder the shot, the rounder the pellet, the truer the flight) and temperature.

 

Premium grade target loads use quality lead shot for dense patterns. Cheaper "promotional" loads use a softer grade of shot, which generate less than optimal patterns. The softer shot that gets deformed at ignition setback and then as it travels through the forcing cone down the bore and then constricted through the choke, tends to fly away from the center of the target and you get what are known as "flyers." Shot size is another factor that will vary pattern density with different choke sizes. Most chokes handle the smaller size shot equally well, but as shot size increases, patterns may change. Some bores/chokes will simply not pattern well with a specific size shot. Or as the weight of the payload increases, so too do patterns alter. Hence the need to pattern everything you intend to try on the clay range or hunting field. Just as you see variances with different buckshot sizes and erratic patterning, so too will you see variances with shot sizes in the #6 up to #2 range. And the larger steel shot sizes are an entirely different animal and a different set of rules apply here altogether.

 

Cold air, being denser than warm air will affect shot as it tends to open patterns up. Late season hunters and clay target shooters may switch to a tighter choke once temperatures drop below 40 degrees.

 

One thing to do once you've established your patterns on the patterning board is cut an outline of your "intended" game and hover it over your target. If there are areas or patches ("voids") that allow your intended game (it could be an edge-on clay target or the outline of a quail) to pass through your pattern unscathed by a pellet hit, that choke is less than optimal and could afford you a miss on the clay range or on the game field. You would need to tighten up your choke for your quarry or up your pellet count.

[djg0770 481]

nevermind

[Pew Pew Plates 358]

Nice write-up.

 

You are correct, most people never extensively pattern their shotguns. That would be akin to never zeroing your sights on a rifle or a pistol. Something unheard of but people do it all the time with their shotgun. With choke tubes today I find more variances than with the older style fixed chokes with their known caveats, so I always approach each as suspicious until I've patterned them.

 

Keep in mind that patterns are also affected by shot hardness (the harder the shot, the rounder the pellet, the truer the flight) and temperature.

 

Premium grade target loads use quality lead shot for dense patterns. Cheaper "promotional" loads use a softer grade of shot, which generate less than optimal patterns. The softer shot that gets deformed at ignition setback and then as it travels through the forcing cone down the bore and then constricted through the choke, tends to fly away from the center of the target and you get what are known as "flyers." Shot size is another factor that will vary pattern density with different choke sizes. Most chokes handle the smaller size shot equally well, but as shot size increases, patterns may change. Some bores/chokes will simply not pattern well with a specific size shot. Or as the weight of the payload increases, so too do patterns alter. Hence the need to pattern everything you intend to try on the clay range or hunting field. Just as you see variances with different buckshot sizes and erratic patterning, so too will you see variances with shot sizes in the #6 up to #2 range. And the larger steel shot sizes are an entirely different animal and a different set of rules apply here altogether.

 

Cold air, being denser than warm air will affect shot as it tends to open patterns up. Late season hunters and clay target shooters may switch to a tighter choke once temperatures drop below 40 degrees.

 

One thing to do once you've established your patterns on the patterning board is cut an outline of your "intended" game and hover it over your target. If there are areas or patches ("voids") that allow your intended game (it could be an edge-on clay target or the outline of a quail) to pass through your pattern unscathed by a pellet hit, that choke is less than optimal and could afford you a miss on the clay range or on the game field. You would need to tighten up your choke for your quarry or up your pellet count.

 

 

Wow, never knew the temp could affect it that much. As far as shot quality goes, I wanted to avoid making the article any longer than it had to be. I mention that you should test every load.... this is why. Also, another thing is when you are calculating pattern density the anitomy of the shot affects how many pellets are in each ounce. I can get significantly more west coast #8 shot pellets into an ounce than I can eagle. However, using the provided numbers should be good enough.

[StephanieSeven 70]

Great write up Glenn! Shotgun is still a pretty abstract concept to me so some of it is a little out of my grasp but very informative. Really liked the information on the choke tube selection. I'm sure I'll pick your brain the more I get into shotgunning.

[axeman_g 128]

+1. Greatjob.

[kenw 293]

Glenn,

 

Thanks so much for taking the time to put this together.

 

I know you've had this in the back of your head for a while, it came together well, and I appreciate you allowing me to use it.

 

K

[glenhunter 0]

Wow, Glen, nice write up. I'm fairly new to shotgunning and hunting and this information will be invaluable to myself. Thank you so much for making it an easy read and soemthing everyone can and should do. Kudos.

 

 

gh

[raz-0 1,259]

Nice write up.

[Regulator72 80]

Nice work, thanks for taking the time to do this

[GoldWolf 0]

This is a very good summary of patterning. I have been shooting for 50 years and it is unreal that even though I have helped pattern guns, I have never really understood why. Amazing. Thank you for such a comprehensive report. I have a lot of work to do.

By the way, I am not a trap shooter, but I have decided to take up the sport. As an older person I do need something to do besides fishing.

[MosinRob 1]

Great write up. Thank you. One question. Why would you pattern from where you think the center is rather than where you aimed? When I'm using the gun I'll be aiming with the sights so wouldn't you want to know the pattern of where it aims?

[El-Groucho 0]

Wow I'm happy this was brought to the top. This is some excellent advice since I'm just starting out!