Shotguns: Understanding Pattern Size and Gauge

Vollmer

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Shotguns: Understanding Pattern Size and Gauge

by Phil Bourjaily
shotgunpattern.jpg


A recent comment to a Gun Nuts post caught my eye: “Shotgun patterns are the same size regardless of gauge.” I have heard that one a lot. Is it true? Well, yes it is . . . but there’s more to it than that.
It is definitely true that the size of a shotgun’s bore has nothing to do with the overall size of its pattern. Air resistance opens patterns, and pellets react to air resistance the same way whether they come out of the barrel of a 12 gauge or a .410.

But . . . generally speaking, the larger the gauge, the more pellets its shells contain. That shell will have a larger effective pattern than a shotshell containing fewer pellets.

Patterns are not evenly distributed. They are denser in the center and sparser on the outside, basically following a bell curve. This is known as Gaussian distribution, after Austrian scientist and mathematician Carl Friedrich Gauss.* Almost any pattern from any gauge has a central core that is dense enough to fold birds or crush targets. That core is usually about 15 inches across. Hit a bird with the pattern core and you’ll kill it, regardless of what gauge you’re shooting or how many pellets your shotshell holds.

However, the more pellets a gun throws downrange, the more pellets there are around the core. Those pellets fill in gaps in the outside of the pattern, meaning you can miss the bird with the center of the pattern and still hit it with the pattern fringe. Therefore a 12 gauge shooting 1 1/8 ounces of shot will shoot a pattern that has more pellets, and fewer gaps around the core, than will a 20 gauge shooting 7/8 ounce, which will beat a 28 gauge shooting ¾ ounce, which beats a .410. Therefore the bigger gauge shooting more pellets has a larger effective pattern even though all the patterns are the same size.

But, you say, comparing larger and smaller bores is apples to oranges because of the difference in payloads. What if they’re all shooting the same amount of shot? Bigger bores still win, at least in theory, because they pattern more efficiently than smaller bores, creating fewer deformed flyer pellets that are completely lost to either the core or the fringes of the pattern. The difference wouldn’t be much in a pure apples to apples comparison, but there would be a difference, and the bigger bores would shoot larger effective patterns.

And that, as Paul Harvey would have said, is the rest of the story.

*Supposedly, Gauss came up with concept of Gaussian distribution while watching recruits shoot muskets at a target.
Photo by Duck Hunting Chat
 


Bed Wetter

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guywhopostsarticlesonshotgunchokes Had a good one awhile back on how shot patterns held together at different distances with different chokes. It was neat. Doesn't matter what choke I use, I'm likely to miss anyway.
 

deleted_account

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guywhopostsarticlesonshotgunchokes Had a good one awhile back on how shot patterns held together at different distances with different chokes. It was neat. Doesn't matter what choke I use, I'm likely to miss anyway.

I think NDA should sponsor our skeet team.... :;:smokin
 

KDM

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Don't do it V!! I've seen some of them guys shoot!! :;:::::;:sorry:;:muahaha

However, I for one am still waiting for the NDA merchandise. These items are becoming a legend such as big foot or nessie. Just Sayin'.
 


snow

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Nice article but flawed,even tho the pattern board shows where your POI is (point of impact) and also gives you a visual of your pattern which is needed to see with different shot sizes and payload what works for your shotgun ,what the article doesn't address is shotstring,not all pellets get to target at the sametime,some aftermarket choke companies excel in the mechanics in shotgun patterns and for the serious shotgunner it gives you a leg up whether shooting targets or in the field.

Just some thoughts~
 

Enslow

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4 buck in my 391 beretta with a modified choke is a beast pig.
 


Kickemup

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I can say I have never checked the pattern on a shotgun. I just shoot the thing if it hits shit I'll stick with it.
 

Enslow

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4 buck works great on zombies and geces. They are both vicious opponents, just ask a coon.
 

Account Deleted

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I can say I have never checked the pattern on a shotgun. I just shoot the thing if it hits shit I'll stick with it.
I spend too much time agonizing over archery stuff to start worrying about shotgun patterning. In golf, I would be a "grip it and rip it" guy for shotgunning.
 


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I'm just about ready to go down the rabbit hole on that one KW. I suspect I will hate myself soon.
 

svnmag

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I respect and understand Guy's article.

John McIntosh proclaims the best constriction/combo/load for upland out to 40yds is CYL/IMPCYL at around 1100fps for a dbl gun. Per SD and other reading: If you choose this combination, you may want to work on your lead and follow-through on clays if you've been shooting speedier loads. The pellet energy difference isn't appreciable at 40 with increased speed and the decreased fatigue (noticeable or not for all the BAMFs) will result with more kills once you wrap your head around the physics.

Of course: A #4 buck will hit harder at 40 than a #2; it's then pattern density becomes the devil with the diminishing freakn' returns. If you would logically like to shoot geces/turkey with large shot; too much choke is bad. It causes shot deformity, decreased pattern efficiency and half-assed flyers which may or may not bring LUCK.

My "school of thought" on turkey is to blow it's head off with a massive amount of small shot from a tight choke.

- - - Updated - - -

I still maintain pre-shotcup M12's shoot like lazers.
 
Last edited:

Kentucky Windage

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I respect and understand Guy's article.

John McIntosh proclaims the best constriction/combo/load for upland out to 40yds is CYL/IMPCYL at around 1100fps for a dbl gun. Per SD and other reading: If you choose this combination, you may want to work on your lead and follow-through on clays if you've been shooting speedier loads. The pellet energy difference isn't appreciable at 40 with increased speed and the decreased fatigue (noticeable or not for all the BAMFs) will result with more kills once you wrap your head around the physics.

Of course: A #4 buck will hit harder at 40 than a #2; it's then pattern density becomes the devil with the diminishing freakn' returns. If you would logically like to shoot geces/turkey with large shot; too much choke is bad. It causes shot deformity, decreased pattern efficiency and half-assed flyers which may or may not bring LUCK.

My "school of thought" on turkey is to blow it's head off with a massive amount of small shot from a tight choke.

- - - Updated - - -

I still maintain pre-shotcup M12's shoot like lazers.

An entire post with no acid trip thoughts in it. You feeling ok?
 


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