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 03-25-2014, 16:09 #1 SHOOTR13 G30SF Owner     Join Date: Jan 2009 Location: PENNSYLVANIA Posts: 215 Understanding Shotgun Chokes... I put this primer together awhile back and thought I would share it here...enjoy ! _______________________________________________ Shotgun chokes were designed to control pattern diameters at different yards. What is a pattern? It is just the grouping of the pellets at a given yardage. This grouping or pattern is measured by a circle diameter. This particular circle must have certain efficiency. In other words, it has to have a certain number of pellets in a given area (called distribution) for it to be labeled an efficient pattern. ================================================== Here is a quick reference chart: Shotgun Choke..... Yardage...........Shotgun Choke Restriction Cylinder................... < 20.......................... 0 Skeet...........................22.5.............. .005 (of an inch) Improved Cylinder....... 25............................... .010 Light Modified...............30...................... .......... .015 Modified....................... 32.5.............................. .020 Improved Modified........ 35................................... .025 Light Full...................7.5.................................... .030 Full....................... 40+................................... .. .035 Extra Full....................40+........................... ..... .045 Super Full.....................40+............................... .055 ================================================== How does a shotgun choke actually work ? There are two forces that tell the story... the mechanical properties while the shot column is in the barrel and the dynamic forces of nature that affect the shot column after it exits the barrel. When the shot column meets up with the choke it forces the column to squeeze tighter together; these forces are called radial forces. Once it is out of the barrel, wind resistance and gravity act on it. When the wind comes into contact with the outside pellets of the shot column it induces spinning and they start to flare off like a ping pong ball with english on it. The tighter the choke the heavier the radial forces, the tighter the pellets are squeezed together so the pattern holds tighter over a longer distance. Conversely, the less restriction you have in the choke the more loosely the pellets are held together and the faster the pattern opens up.
 03-25-2014, 16:10 #3 SHOOTR13 G30SF Owner     Join Date: Jan 2009 Location: PENNSYLVANIA Posts: 215 As everyone here already knows, Shotgun shells are generally measured by "gauge"... though in other locations outside the United States the term "bore" is used with the same meaning. Where as rifles and handguns are almost always measured in "caliber"...which is simply a measurement of the internal diameter of the barrel measured in fractions of an inch and consequently is approximately equal to the diameter of the projectile that is fired. By contrast, shotguns are also measured by "gauge"...which is the weight (in fractions of a pound)...of a pure lead round ball that is the same diameter as the internal diameter of the barrel. For example, a shotgun is called 12 gauge because a lead sphere that just fits the inside diameter of the barrel weighs 1⁄12 of a pound. This measurement comes from the time when early cannons were designated in a similar manner...a "12 pounder" would be a cannon that fired a 12 pound cannonball, thus inversely, an individual "12 gauge" shot would in fact be a 1⁄12 pounder. Thus, a 10-gauge shotgun has a larger-diameter barrel than a 12-gauge shotgun, which has a larger-diameter barrel than a 20-gauge shotgun, and so forth. Shotshells are loaded with different sizes of shot depending on the target. For skeet shooting, a small shot such as a # 8 or #9 would be used, because range is short and a high density pattern is desirable. Trap shooting requires longer shots, and so a larger shot, up to #7½ would be desired. The smaller the shot (#9 for example)...the more receptive it will be to being constricted or "choked" than larger shot (say #4) due to space for displacement within the load. For hunting game, the range and the penetration needed to assure a clean kill must both be considered. Shot loses its velocity very quickly due to its low sectional density and ballistic coefficient. Small shot, like that used for skeet and trap, will have lost all appreciable energy by 100 yards or meters, which is why trap and skeet ranges can be located in relatively close proximity to inhabited areas with negligible risk of injury to those outside the range. Birdshot sizes are numbered similar to the shotgun gauges; the smaller the number, the larger the shot. For hunting, shot size must be chosen not only for the range, but also for the game. The shot must reach the target with enough energy to penetrate to a depth sufficient to kill the game. Lead shot is still the best performer for the money, but environmental restrictions on the use of lead, especially with waterfowl, require steel, bismuth, or tungsten composites. Steel, being significantly less dense than lead, requires larger shot sizes, but is a good choice when cost is a consideration. Steel, however, cannot safely be used in some older shotguns without causing damage to either the bore or to the choke of the shotgun due to the hardness of steel shot. Since tungsten is a very hard metal, it must also be used with care in older guns. Tungsten shot is often alloyed with nickel and iron, softening the base metal. That alloy is approximately 1/3 denser than lead, but far more expensive. Bismuth shot falls in between steel and tungsten shot in both density and cost.
 03-25-2014, 16:11 #5 SHOOTR13 G30SF Owner     Join Date: Jan 2009 Location: PENNSYLVANIA Posts: 215 BTW...some chokes are measured in micrometers...my 1st list (above) is showing fractions of an inch. ================================================== Here's a list that breaks that down: Micrometers..................Inches..................American Name 0................................... .000......................... Cylinder 127................................ .005......................... Skeet 254................................ .010......................... Improved Cylinder 381..................................015.......... ............... Light Modified 508................................ .020......................... Modified 635................................ .025......................... Improved Modified 762................................ .030......................... Light Full 889................................ .035..........................Full 1143.............................. .045......................... Extra Full 1270.............................. .055......................... Super Full ================================================== Last edited by SHOOTR13; 03-25-2014 at 16:12..
 03-25-2014, 16:12 #6 SHOOTR13 G30SF Owner     Join Date: Jan 2009 Location: PENNSYLVANIA Posts: 215 This chart will give an idea of what choke to use at what yardage for sporting clays... with the caveat that ammo, intended target, angle of presentation ( front, back, side ) also weigh in on the equation... ================================================== ========= Red - Pattern too small | Yellow - small but usable | Green - Optimal Pattern ================================================== ========= Choke Tube Selection: Choke tube selection is a confusing issue amongst a lot of shotgunners but one that is easily explained. The real reason you want the right choke is to be able to place at least 70% of the shot in a 30" circle at 40 yards... the minimum / maximum pattern kill zone... meaning the pattern will cleanly kill anything in this circular zone. Selecting the correct choke tube is nothing more than moving that same exact pattern to different yardages. In other words... if you want to shoot at a target 20 yards away then select a choke tube that gives you 70% of the pattern in a 30" circle at 20 yards...same if shooting at a target that is 45 yards away, select a choke tube that will give you 70% of the pattern in a 30" circle at 45 yards. Extra Full Choke: ...................delivers a 70% pattern at 45 Yards. Full Choke: ............................delivers a 70% pattern at 40 yards. Modified Choke: ....................delivers a 70% pattern at 35 yards. Improved Cylinder Choke: ....delivers a 70% pattern at 30 yards. Cylinder Choke: ....................delivers a 70% pattern at 25 Yards.
 03-26-2014, 18:13 #7 CarolinaKat Senior Member     Join Date: Apr 2003 Location: NC Posts: 217 Gunnutz13 Thanks for the good info. Tell me does this info (constriction, range, etc.) only specifically apply to 12 GA? Or generally is the data also the same say for 20 GA? Dan __________________ "If you are 35 years old and you are not a Republican, ...er no change that to Conservative, you have not done anything with your life"
 03-27-2014, 15:44 #8 Sgt_Gold Senior Member   Join Date: Jul 2006 Location: NY Posts: 512 This is excellent information and should rate a sticky.
 03-27-2014, 19:11 #9 GLOCK+ Member   Join Date: May 2009 Posts: 43 Excellent. Very useful information. I too recommend this information to be classified as sticky. GLOCK+
 03-27-2014, 19:14 #10 GLOCK+ Member   Join Date: May 2009 Posts: 43 GUNNUTZ13: I really thank you for sharing this information. GLOCK+
 03-27-2014, 20:00 #11 j4nelli Registered User   Join Date: Jan 2014 Posts: 16 Good timing as I just tried trap for the first time on Sunday. I had a choke that was not constricted enough (I think it was improved cylinder) and I didn't have any others with me. I put in the improved modified and am going back out tomorrow to try again.
 03-28-2014, 03:57 #12 Deployment Solu Kydex Crafter     Join Date: Jul 2007 Location: Arkansas Posts: 6,045 Blog Entries: 1 Thanks! Excellent!! __________________ Federal, State, and NRA Certified Firearms Instructor, Arkansas CHL Instructor. Handgun, Shotgun, Patrol/ Urban Rifle Instructor. Advanced Tactics Instructor. The world needs less victims and more victors!!!!!
 03-28-2014, 05:21 #13 Jaysonics Member     Join Date: Jan 2014 Location: Central MA Posts: 38 Really good info. Saw this the other day on Remington owners.Com. Wish that site was more active. Just picked up an 870 tactical and will be bookmarking this page to help me pick out different choke tubes. Thanks!
 03-28-2014, 14:42 #14 collim1 Shower Time!     Join Date: Mar 2005 Location: USA Posts: 9,948 Lots of great information in there, thanks for posting. I think many people have a hard time understanding chokes, and many more think chokes are a magic solution. I have found in my own testing by hanging up old bed sheets and patterning at different ranges that tighter is not always better, and the quality of the shell being fired seems to have more impact on pattern than changing chokes in many cases. One book I read growing up, and have read many times since is this one: Despite its age it is still relevant and IMO is a shotgunner's bible. If you are interested in becoming a better shotgun shooter it is definitely worth the read.
03-28-2014, 15:03   #15
jakebrake
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Quote:
 Originally Posted by Sgt_Gold This is excellent information and should rate a sticky.
I second that.
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 03-29-2014, 08:11 #16 Big Bird NRA Life Member     Join Date: Aug 2003 Posts: 10,039 The one thing I will add to the above posted information is--that's the theory. The actual experience one has with a given choke and given load CAN AND WILL vary dramatically from the theory. There is no getting around the fact that you need to pattern your shotguns. Its probably one of the most boring tasks in the world--shooting big sheets of paper and counting holes. But you will never know how a given load patterns in a given gun unless you shoot it on paper at the distances you expect to encounter. Manufacturers have tremendous variation in bore diameter, length of forcing cones, choke restrictions etc. And a choke restriction is RELATIVE to the bore diameter. For example...you can have a Modified choke restriction of .020" But that's relative to the bore diameter and if you buy a screw in choke that varies from the gun maker in terms of bore diameter you can have more or less choke than .020..... Furthermore, some ammo technology such as Federal's Flite Control wad uses the wad to control pattern not choke. In fact if you were to shoot a flite control shell through a full choke you would get really open and uneven patterns not the tight pattern you would be expecting. All the above information is interesting but until you actually put your ammo on paper you are only guessing and in my experience the results can be dramatically different than the theory. __________________ Big Bird, “Est Nulla Via Invia Virute” Last edited by Big Bird; 03-29-2014 at 08:12..
 03-29-2014, 08:16 #17 ColdSteelNail Senior Member     Join Date: Dec 2011 Location: North Georgia Posts: 1,484 I would argue that wind resistance and gravity are working on the shot column BEFORE it exits the barrel. Sorry, just being a smart ass but it is true.
03-31-2014, 12:48   #18
Leigh
Senior Member

Join Date: May 2000
Location: Eastern Kentucky
Posts: 5,356

Quote:
 Originally Posted by Big Bird There is no getting around the fact that you need to pattern your shotguns.
So true.

For HD uses (i.e. cylinder bore), it matters very little; for hunting/sporting shotguns, it matters A LOT!

Years ago, I sold a friend a shotgun (Remington 870 Special Field). A few weeks later he brought it back to me and said, "This shoots low and left, terribly."

I had my FFL at the time (he bought it NIB from me) so I decided to send it back to Remington.

Sure enough it was indeed "off." The screw threads in the barrel (Rem-Choke) were misaligned just enough and his claims were justified.

To Remington's credit, they replaced the entire barrel/choke tubes and even sent a 40-inch patterned target back with the new barrel!

 03-31-2014, 12:58 #19 Berto woo woo     Join Date: Sep 2003 Location: WA Posts: 28,661 Great info and probably a good general guideline. I patterned a gun recently, the patterns with the two loads I used were consistent with what I expected from the two barrels and chokes used.....but patterning was the only way to know for certain what was happening with those specific loads from this specific gun. __________________ ...Then I found a place it's dark and it's rotted it's a cool, sweet kinda-place where the copters won't spot it. -T Hip
03-31-2014, 16:31   #20
Big Bird
NRA Life Member

Join Date: Aug 2003
Posts: 10,039
Quote:
 Originally Posted by Leigh So true. For HD uses (i.e. cylinder bore), it matters very little; for hunting/sporting shotguns, it matters A LOT! Years ago, I sold a friend a shotgun (Remington 870 Special Field). A few weeks later he brought it back to me and said, "This shoots low and left, terribly." I had my FFL at the time (he bought it NIB from me) so I decided to send it back to Remington. Sure enough it was indeed "off." The screw threads in the barrel (Rem-Choke) were misaligned just enough and his claims were justified. To Remington's credit, they replaced the entire barrel/choke tubes and even sent a 40-inch patterned target back with the new barrel!
Actually, you would probably be shocked if you saw buckshot patterns for various loads at 10-20 feet. Take a load of Winchester Ranger 2 3/4" #4 buck and pattern it vs say a Federal Tactical load of OO with a Flite Control wad and get back to me...
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Last edited by Big Bird; 03-31-2014 at 16:32..

 04-02-2014, 12:03 #21 SHOOTR13 G30SF Owner     Join Date: Jan 2009 Location: PENNSYLVANIA Posts: 215 Gentlemen... The above info was posted as a primer and a guideline...but as others have added, it is subject to your choice of ammo in your particular firearm with your brand of choke during the patterning process. YMMV... Enjoy.
04-02-2014, 20:31   #22
MarkCO
CLM Number 245

Join Date: Dec 1998
Posts: 6,791
Quote:
 All the above information is interesting but until you actually put your ammo on paper you are only guessing and in my experience the results can be dramatically different than the theory.
Very true.

I have sets of data with Rem 1100s, VersaMaxs, M2s, Brownings and SLPs from 5 yards to 40 yards with different choke brands and birdshot and buckshot. You can see as much as a 30% difference in patterns just by switching a gun, choke brand or load. As Big Bird said, there are Flite Control wads as well as spreader wads so you can effect some pretty serious change from one choke just by changing loads if you know what you are doing.

As for barrel length, You can not give me a shotgun with a barrel longer than 26". 22 to 24" is the do-all length for me. Backboring, chrome lining and other enhancements can affect performance significantly. With the modern powders, there has been testing to show that past about 24", there is no actual added performance of the shot column.

The one HUGE glaring thing missing in the OPs writing is fit. The shotgun must fit you in order for you to hit, be able to call your shots. Avid shotgunners get their shotguns fit while few general shooters ever bother. Just one more reason I really like the VersaMax...it makes it easier for the average Joe to shoot a properly fit shotgun. I will take a well fit 18" pump with a Mod choke over an ill fitting anything with a complete set of chokes everyday of the week. Well fit shotguns feel like they kick less, swing better, let you hit better, and you just start to feel right about them. Much more important than chokes.

Another topic of some interest is the length of the shot column. The faster loads tend to have a longer shot columns while the reduced recoil loads have a shorter shot column than standard loads. This can have an effect on actual pattern density in the 3D world, especially with thrown clays. The 2D pattern board is but one measure of pattern density.
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Last edited by MarkCO; 04-02-2014 at 20:33..

04-02-2014, 22:16   #23
Big Bird
NRA Life Member

Join Date: Aug 2003
Posts: 10,039
Quote:
 Originally Posted by MarkCO Very true. The one HUGE glaring thing missing in the OPs writing is fit. The shotgun must fit you in order for you to hit, be able to call your shots. Avid shotgunners get their shotguns fit while few general shooters ever bother. Just one more reason I really like the VersaMax...it makes it easier for the average Joe to shoot a properly fit shotgun. I will take a well fit 18" pump with a Mod choke over an ill fitting anything with a complete set of chokes everyday of the week. Well fit shotguns feel like they kick less, swing better, let you hit better, and you just start to feel right about them. Much more important than chokes. .
While shotgun fit is critical on bead sighted shotguns that are used by shooters firing like a sporting shotgun. It kinda makes the case for putting a set of ghost rings on a HD shotgun.

Head position is critical on a beaded shotgun because your eyes essentially are your rear sight. And while they may come to the correct position behind the barrel when you mount the gun in a classic standing position what about in all the other positions? Do it from the prone or from sitting or barricaded next to a doorframe... You head will change position dramatically which also means your eyes (rear sights move) by more than a 1/2 depending! That will dramatically change the point of impact of the rounds--how can it not? But you might say...well Big Bird...no big deal its a shotgun and we will more than make up for it with the pattern.

But anyone with any experience knows there is a very small pattern with most any shotgun shell inside of ten yard--it essentially works like a big single projectile. Which means you need MORE accuracy not less. Think of it this way...it its no big deal why don't we put beads on our ARs, take off the rear sights and shoot them like shotguns? I mean darn...it would be quicker right? And certainly accurate enough even though your rear sight may vary by 1/2" in its position relative to the front sight... I mean an AR with a rear sight that moves around in a 1/2" arc would be plenty accurate for a AR at 10 yards right? Yeah.....sure...make that case sometime.

But that's exactly the case we make for people to shoot beaded shotguns vs guns equipped with ghost rings.

If you think it doesn't matter you've never missed the low bird from station 8 on the skeet field because your gun mount was off...(meaning your rear sights weren't aligned properly)

Gun fit is everything if you shoot a shotgun from a traditional standing position squared off with the target. Its meaningless on a HD shotgun barricaded behind a dresser in a bedroom. Meaningless because you can't get the gun into the same position behind your eyes and your point of impact will shift as you move from body position to body position.
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 04-03-2014, 16:58 #24 MarkCO CLM Number 245 Charter Lifetime Member     Join Date: Dec 1998 Location: Colorado Posts: 6,791 Excellent follow-up Big Bird. __________________ Good Shooting, MarkCO .40 S&W Club #1, 1911 Club #1067 NRA Life Member and Certified Instructor www.CarbonArms.us

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