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Posted By: Vol423 What is the ideal convergance of SXS barrels? - 05/04/13 01:40 AM
If an exceptional gunmaker were to produce his most perfect set of barrels, what would the convergence pattern be at various distances? Would the barrels shoot closer together until they reach their convergence distance, then cross and spread apart at longer range? What would that ideal picture be at 10, 20, 30 40 50 and 60 yards? What is the optimum convergence distance for a 12 gauge upland gun?
Can't answer that, but, I know that the 303s on a Supermarine Spitfire were set to 300 yards.
Wouldn't "optimum convergence" be a bit of a moving target, pardon the pun? I suspect it would differ a bit between a gun primarily intended for pursuit of ruffed grouse in eastern MN/western WI, versus a gun primarily used for pass shooting sea ducks of the coast.

Best,
Ted
The book L C Smith Plans & Specifications gives the convergence of 12 & 20 ga FW bbls.
They are listed as follows;
12ga
Bbls comverge at the rate of .0113" per inch or an angle of 0░38'.
For a 30 bbl having a 1.156" spacing of C/L's at breech & .8175" at muzzle the axises of the bores would converge at 72.452" from the muzzles. At 40 yard the would be separated by 15.453". These Axis lines would of course cross after passing the convergence point.
For the 20ga with 28" bbl the convergence is given as .011" per inch, a convergence point @ 63.09" from muzzle & seperation of 15.146" @ 40yds.
Understand this is simply where the bbls are "Pointed" this does not mean this is where they are going to hit when fired.
Originally Posted By: Vol423
What is the optimum convergence distance for a 12 gauge upland gun?


Well, lessee. What is the exact distance at which all birds are shot when upland hunting? And to complicate it further, what exact load do these upland hunters use? Can't have loads of differing recoil, now. It will mess it all up.

I kill all my doves at exactly 22 yards, as incomers, using a 20 ga. with 2 1/2 - 7/8 - 7 1/2. I shoot all my quail going away at exactly the same distance, so this should be easy, eh? All we need now is that exceptional gunmaker.

No, wait. I think I want my right barrel to hit dead on at 22 yards, but my left to be on at 38. And I think I want the right barrel regulated with the 7/8 oz. load and the left for a 2 3/4 - 1 oz. load, which means the angles of convergence must be different.

Oh, bother! Maybe I'd be better off just letting that gunmaker build it like he wants to.

SRH
The old time gunmakers were just as opinionated and stubborn about their ideas of convergence as we are today. Each maker had what they thought was the proper amount of convergence built into their guns. From shooting huge amounts of shells at pattern paper, I can deffinitely tell you that upland guns were set to converge somewhere between 20 and 25 yards, but heavy waterfowl guns were meant to converge at 40 yards or more. There was really no set amount of convergence rate.
The rates listed for the Feather Weight L.C.'s is certainly correct, but that doesn't refleck on any other guns or makers. As stated before, that just tells you where they are pointed while at rest, and has nothing to do with where they will be pointed at the moment the shot leaves the barrels. The points of impact have to do with many different factors such as the load being fired, the weight of the gun, the length of the barrels and the amount of time the load is in the barrel,the general build of the shooter,etc. As you can see, the gunmakers were working with averages, for the loads fired in their guns, the expected game, and the antisipated distance that it would be shot at, and the general build of the people who were going to buy and use one of their guns.
I think you know that there is no one answer to your question, but this just touches on some of what affects the shot placement and convergence problems faced by gunmakers everywhere. Bob
Miller's post tells it all. Shotgun barrels, about an inch apart at the muzzle, do not converge. They go out straight as arrows, an unmeasurable one inch apart. If even a minute convergance is built in, as in Miller's example, the patterns are feet apart at longer shooting ranges. Can any of you measure an inch of difference at the pattern board. I can't.
I had always heard convergence at 40 yards was standard. Parallel barrels that never cross is for double rifles only?
Actually, it's my understanding that double rifles are built to converge. Usual range, I think, is somewhere in the neighborhood of 75 yards.
Some say yes others say that they should not . Shotgun barrels are made so that the barrels tubes come together at the muzzles . Centers at the breech varied so the convergence was never a real consideration .
You can work it out mathematically by taking the centers at muzzle away from the centers at breech and dividing that by the length of the barrel to give the taper .This can the be projected to find the cross over point . In my experience experimenting with lasers at 30 yard the right barrel will shoot to left of center and the left to right of center . To make a pair of shotgun barrels that have over lapping patterns at 30 yards the barrels at the muzzle would have to be spaced about 5/16"to 3/8 "on a 28 inch gun dependent on the center at breech .
Originally Posted By: Vol423
If an exceptional gunmaker were to produce his most perfect set of barrels, what would the convergence pattern be at various distances?

If he were "exceptional", he would ask what you were going to do with the gun, and at what distance you wanted to have them hit. IMO.

Originally Posted By: Vol423
Would the barrels shoot closer together until they reach their convergence distance, then cross and spread apart at longer range?

Yes.

Originally Posted By: Vol423
What would that ideal picture be at 10, 20, 30 40 50 and 60 yards?

That depends on what the customer wanted. Most of us get what we get, which is whatever the gunmake decides and whatever his effort results in. I think the commonly accepted goal is 40 yds.

Originally Posted By: Vol423
What is the optimum convergence distance for a 12 gauge upland gun?

Some of that depends on whether you hunt a flushing dog or pointing dog or just walk up birds. My preference for an upland gun would still be the common 40 yds...because, as Bill pointed out, who can tell an inch or two on the pattern board...and it becomes more important as distance increases that your POA is close to your POI.



As Birdman stated, a shotgun moves left and right when the gun is fired. As the gun moves, the shot is traveling down the barrel. Where the barrel is pointed when the shot leaves the barrel is what determines where it will hit. That's why a common .011 convergence would have the static (gun at rest) crossing point of the barrels at about 9 ft, but that obviously isn't where they hit when fired.
Obviously if you were firing a 10 Mag load of 2oz from a 7lb gun you would need more convergence than if firing a .410 Żoz load from a 10lb gun. That big load from the little gun is simply going to move it around more than the little load from a big gun. If you don't believe that "SHOOT" each of'em.
Barrel convergence is speaking of the mechanical alignment of the bores axis. When you are speaking of converging at 40yds, 75yds etc this is not the mechanical convergence of the bbls but where they are "Destined" to hit together.
When you figure the mathimatical convergence it will work out more than the actual convergence because the firing the right barrel will move the barrels slightly to the right and the left slightly to the left negating the mechanical convergance putting one pattern right on top of the other if the shotgun was build around an average load. Unless the barrels were very crudely built I suspect that patterns will be nearly on top of each other at least to the effective range of the load.
Thanks for the input. I was expecting to see information about how the two barrels centered their patterns relative to each other at various ranges. I keep missing with my tight barrel and I'm wondering if the barrels do not shoot close enough together. I shoot left handed. I shoot the left barrel first and it shoots where I look. The right barrel's pattern is centered 8 inches to the right of the left barrel's pattern center at 20 yards. I haven't tested other distances in detail yet but the left barrel appears to be spot on at 40 also. I used full chokes for both barrels.
Vol, didn't you mean to say that you keep missing with the right barrel?

If the right barrel's pattern is centered to the right, it may be that it will be regulated for a longer distance than 20 yards. It just may not have "gotten to the centerline" yet. Back up to 30, and 40 and see. Sometimes this is the case. With full choked barrels, it would be more useful for them to be regulated out closer to 40 than at 20, anyway.

I've got a double that I have got to move the center of the pattern over 8 inches as well. But, it's left barrel shoots 8 inches right of POA at 25 yards. IOW, it's already crossed the "centerline", and only gets worse at longer distances. I still kill a lot of doves with it, but know it is causing me some misses, and lots of non-centered hits.

SRH
You guys are quite entertaining. If the two barrels are one inch apart at the muzzle, they should be one inch apart to infinity with no need to worry about convergence because no one can tell the difference between a pattern that is 1/2" to the left from the left barrel and 1/2" to the right for the right barrel. Why should they converge? The shot comes straight out of the muzzle and goes straight to infinity except for the drop caused by gravity.
I simply fail to Understand how anyone who has obviously looked at a lot of double barreled shotguns can make such a statement as this. I may be a bit slow at times but I'm not Blind. It is patently obvious the two barrels of a double "CONVERGE" toward the muzzle, they are "NOT" set parallel. The convergence is not for what line the shot travels After it leaves the muzzle, but Just Exactly where the muzzle is pointing at the time of exit. After it leaves the muzzle it travel is only affected by Gravity or Wind Drift. Be it Shot or Ball however not projectile fired from a gun having any perceptible amount of recoil leaves a shoulder fired gun from a static position. It matters not whether you are swinging the gun or taking a Dead Aim from one held stationary. The gun "WILL" Move from the time the trigger is pulled prior to the exit of the projectile/s. That is Why the barrels of a Double Converge. If they did not, the Right bbl would shoot to the right & the left one would shoot to the left & it'd be a lot more than the distance between them. Even my old Cap Lock ML'er with both cylinder bored bbls have converging barrels to better center the patterns.
Bill, I think maybe you're forgetting that, using your example of 1" at the muzzles, if they are 1" apart at the muzzle (center to center) they will be somewhere around 1.340" apart (center to center) at the breech, for a 12 ga. that is. This .340" difference from breech to muzzle would be the amount of convergence.

SRH
Originally Posted By: eightbore
You guys are quite entertaining. If the two barrels are one inch apart at the muzzle, they should be one inch apart to infinity with no need to worry about convergence because no one can tell the difference between a pattern that is 1/2" to the left from the left barrel and 1/2" to the right for the right barrel. Why should they converge? The shot comes straight out of the muzzle and goes straight to infinity except for the drop caused by gravity.


Show us a picture of your double that has a 1" space between the barrels at the muzzle.

Best,
Ted
Ted, try measuring a 12ga, center of one bore at the muzzle to center of the other bore. I think you'll find pretty close to 1" separation.
"Vol, didn't you mean to say that you keep missing with the right barrel? "

The right barrel is the tight barrel, or at least that's the way I have it set up. It has screw chokes. I sent the gun back to the manufacturer for correction. The problem was the choke tube threads in the right barrel. According to them, the barrels now shoot together at 25 yards. Their standard, by the way is for the barrels to shoot together at 25 yards. I'm not going to mention the make because that would turn this discussion into a tirade for and against that brand name.

The only other time I've seen this much separation was an AYA No 4 Deluxe I had that was a true left hand gun. I couldn't hit targets with the right barrel on that gun either.

I'm going to do some additional testing at 25 yards when the gun returns. 25 yards is far enough away to show a trend without having to resort to multiple shots at the same aiming point to reveal the pattern center. Right now I have a good inventory of English and European doubles for testing also.
Originally Posted By: L. Brown
Ted, try measuring a 12ga, center of one bore at the muzzle to center of the other bore. I think you'll find pretty close to 1" separation.


I know that, Larry. I was just having some semantic fun with it.

Best,
Ted
Having examined hundreds, if not thousands of doubles, it is obvious that barrels converge. It is also obvious that convergence is not as critical as in rifles, and this can be concluded by the fact that regardless of barrel legth or gauge the barrels touch at the muzzle. In fact you can tell a chopped double by the lack of muzzle to muzzle contact.

As long as the patterns hit to the same point of aim at the required distance there is no need to work out the trigonometry of the thing.

More serious fault in barrel alignment is the vertical deviation as this can be a cause of regular and puzzling misses.
My Ca 1890 32" bbl'd 10lb 10ga Lefever undoubtedly has the widest set muzzles of any shotgun I have ever owned. Per a nice set of Starrett dial calipers measuring the closest point between the bores & then their widest point & striking an average they have a Cl/CL spacing of .915". As the OD's of the muzzles measure an even .900" that means they actually have an .015" spacing between the barrels. As they are still a full 32" long & there is no other indication I purely doubt they have been cut. They are however still a good bit shy of 1" spacing & they "Don't Touch". I didn't check the breech CL's but it is a large frame gun & they are rather wide.
For a British 12ga the following would be typical,Firing Pin centres 1 &1/8th apart (1.125") Muzzle diameters .800" with tubes touching.Thus centres would be .800" Total convergence rate of .011" - .012" per inch of barrel length. Bore Centre lines will intersect at 6-7' from muzzle. Upon discharge gun will undergo degree of torque rotation in direction of discharging bbl , ie Right pulls right, left pulls left. Impact will centre on line of sight along rib.
Actual pattern centre could not be identified accurately enough to express any convergence.
The gunmakers goal would be to have both patterns superposed over each other at 40 yds. The very theoretical incompleted convergence of 4/10ths of an inch at 20 yds would be impossible to measure
Extremely Well Said Mr Lomas. That
Quote:
Upon discharge gun will undergo degree of torque rotation in direction of discharging bbl, ie Right pulls right, left pulls left.
seems to be what so many are not grasping. Thus the two bbls do not both hit point of aim at 40yds because that is where they are Both statically pointed prior to discharge, but that is where they are individually pointed as the shot exits muzzle.
Saying all muzzles are together is a generalization.
Yep. I was surprised when my new 16 ga. RBL was delivered a few years ago with about 1/8" separation between the muzzles. I checked with CSMC, they confirmed this is per the design. Approximately 27/32" between bore centers at the muzzle and 35/32" at the breech. Several patterns shot at 30 yds. hit where they should, so I don't think about it any more.

Jay
This is my first post on the forum, so I might as well jump into a subject that has given me fits. I am a turkey hunter and live in Alabama where we have a generous spring season limit and lots of turkeys. I've always loved a good sxs, but had never used one for turkey hunting except for one season back in my youth.

I have been thinking for some time that the perfect turkey gun would be a sxs 20 gauge shooting the heavy tungsten shot. With one open barrel for close shots, and one tight barrel for longer shots, every possible shot should be covered. I also needed to be able to mount some type of sight on the gun. My eyes are too bad to get by with beads, so I wanted to be able to mount a Burris FastFire on it.

Obviously, you don't walk into the gun shop and buy a monstrosity like this, so I knew it would be a project. I settled on a Yildiz; it was the lightest double available because of the alloy receiver, but the downside was that it only came with a single trigger. I can select the barrels easily, but nothing is as fast as a double trigger.

I first determined that both barrels shot to the same POA, and they did very well. I sent it to my gunsmith and he did a great job of creating my dream gun. He cut the barrels to 24" and rethreaded, opened the forcing cones, shortened the stock and added a quality recoil pad, and did a great job of mounting the sight. He also made 2 turkey chokes.

I shot the gun with light field loads when I got it back and both barrels centered well at 25 yards. Then I shot my heavy 1.75 oz tungsten turkey loads and found I had a problem. The left barrel shot 10" to the left at 40 yards, and the right barrel shot 7" to the right. It was only then that I started to get serious learning about barrel regulation of a sxs. I found that its impossible to get a sxs that will shoot all loads with both barrels to the same POI. You have to regulate the gun to shoot one basic load, and all others will be off somewhat.

In the case of the Yildiz, it is regulated to shoot light field loads and does it very well. It was not made for what I wanted to do. I was able to load some lighter shells that produced POIs that were about the same for both barrels, but I wasn't satisfied. I sent it to Brileys and had them make eccentric chokes for the heavy loads. It took them 2 tries, but they made it usable.



Its proven to be a very good turkey gun, and at 5 lb 2 oz is a dream to carry. It balances right at the receiver and now comes close to being the perfect turkey gun. I won't call it perfect because of the lack of double triggers, and the pattern on the tight barrel is not as good as I would like.

So my search for the perfect turkey gun continues. I don't think anyone makes one like I want, so I am probably out of luck.
Welcome Coosa. That's a nice bird and your story about the trials of getting it to shoot where you wanted it to was interesting. A number of the guys here are using .410s with that tungsten shot. I'm still using lead but the idea of changing over to an ultra-light gun is intriguing...Geo

P.S. On the other hand how dead do you need'em to be?
Originally Posted By: Geo. Newbern
Welcome Coosa. That's a nice bird and your story about the trials of getting it to shoot where you wanted it to was interesting. A number of the guys here are using .410s with that tungsten shot. I'm still using lead but the idea of changing over to an ultra-light gun is intriguing...Geo

P.S. On the other hand how dead do you need'em to be?


Thanks for the welcome! Yes, I am aware of several hunters using tungsten in a .410, and they are as effective as 3.5" 12 gauge guns shooting lead. Its amazing stuff. When I first started working with it 5 years ago, I developed a 3.5" load for my Super Black Eagle and have shot a bunch of turkeys with it. I eventually realized it is overkill to fire 2 oz of this stuff at 1250 fps at a turkey. The 1.75 oz 20 gauge load at 1100 fps will kill one further than I would shoot him, but the modified barrel of the Yildiz gives me such a big killing pattern that an old man like me can really use.

Are there folks using it in a .410 sxs? That would be a really interesting combo! I killed my first squirrel at age 9 with a borrowed Winchester .410 sxs and have loved the sxs ever since. The gun belonged to a neighbor, and he offered to sell it to my dad for $40. I begged for the gun, but he said it was too much. What would it be worth today? Something like $3k from what I can gather. Oh well.
Vol423,
It was I believe standard practice in the British gun trade to set the convergence of 12G barrels at 40 yards. Packing blocks are made to space the barrels during the manufacturing process so as to guarantee the point of impact.
In the case of the double rifle, in particular large calibre ,the point of impact was set at 100 yards. Once again guaranteed by the use of packing blocks during manufacture.
[IE: I recognise that in the case of the double rifle regulation may be required despite the use of packing blocks]
I recall that years ago when visiting H&H they had on display a very large block of teak sectioned to show two bullets entering the block and impacting on one another.The bullets were said to be fired from a fixed bench rest at 100 yards.
Roy;
Don't want to seem overly picky but the first part of your statement doesn't jive with the 2nd part. The bbls themselves were Not set to converge at 40yds, they were set to have the patterns impact together at 40yds. As has been well pointed out by several in this long thread the bbl's axis themselves are set to converge very close to 2 yds (between 6&7 feet).
Originally Posted By: coosa
[quote=Geo. Newbern] The 1.75 oz 20 gauge load at 1100 fps will kill one further than I would shoot him, b



I'm thinking that I would not want to shoot a 1 3/4 oz load in a sub-6# gun. Flinch city, here we come!
Maybe a .75 oz load?
Originally Posted By: L. Brown
Originally Posted By: coosa
[quote=Geo. Newbern] The 1.75 oz 20 gauge load at 1100 fps will kill one further than I would shoot him, b



I'm thinking that I would not want to shoot a 1 3/4 oz load in a sub-6# gun. Flinch city, here we come!


Larry ya gotta be careful with that quote and paste stuff; that ain't my words. I would not want to suffer the recoil of that load either...Geo
2-piper
Recommend that you refer to "The Modern Shotgun,"Vol,1 by Major Sir G Burrard, pages 31-35. These pages review the need for shotgun barrels to converge at 40 Yards so as to hit at the same spot. Also seen are illustrations of correctly designed barrel spacers.
William Greener in his book, "The Gun" 1834,also discusses the need for shotgun barrels to Converge.
Roy, you're missing a difference in careful definition of terms -- barrel convergence being where the bore lines cross, not where shot patterns hit. Burrard may not have made the distinction, but it's been drawn in this thread. Jay
This topic reminds me of the patterning thread in some ways.

The convergence of a production gun is done by dimensional control of what the maker developed and validated on a prototype just as virtually all chokes in production guns are machined to dimensional specification rather than individually tested and developed.

The maker chose the load for convergence testing and also chose the shooter(s), whose individual physical characteristics can affect POI. Even the H&H video showed an employee shooting for POI rather than the customer of the bespoke gun. It must work out well a high percentage of the time or they'd do it differently. But there was a recent post about a bespoke gun that hit off target by enough to perturb the customer.
If the POIs remained parallel out to infinity that would be just as acceptable as them converging at 40 yards. What is the difference in the muzzle centerlines of a 12 gauge SxS - 0.9 inches?

I used the "Shotgun Insight" program to anyalyze somewhere around 200 patterns, including POI. I shot 20 rounds out of each barrel freehand. The average POIs for each barrel were typically a minimum of 6" apart at 40 yards, both for SxSs and OUs. It is also very likely two shooters shooting the same gun would get different POIs.

There is no inherent need for convergence of the POIs at 40 yards. And divergence is probably the norm.

Best,

Mike
Originally Posted By: Geo. Newbern
Originally Posted By: L. Brown
Originally Posted By: coosa
[quote=Geo. Newbern] The 1.75 oz 20 gauge load at 1100 fps will kill one further than I would shoot him, b



I'm thinking that I would not want to shoot a 1 3/4 oz load in a sub-6# gun. Flinch city, here we come!


Larry ya gotta be careful with that quote and paste stuff; that ain't my words. I would not want to suffer the recoil of that load either...Geo


Sorry about that, George. You'd responded to Coosa, who was the guy who said he used the 1 3/4 oz load.
The barrels on a Darne slug gun are regulated to 55 yards. I found it interesting that the customer who ordered the single one I sold was asked to specify what chokes he wanted (Darne slug guns are considerd true dual purpose guns) and after the chokes were cut, the gun was regulated.
The gun was equipped with a folding leaf rear sight, and a partridge bead on a ramp in the front. When fired with Federal slugs (it had been regulated with Federal slugs, in France, if I recall correctly) the black center of the target had two holes that looked like a pair of eyes looking back at you. It handled fine birdshot very well out to about 35-40 yards.
Yes, the barrels had to converge to do that at 55yards. At longer ranges, the slugs would have eventually crossed paths
Wes Gilpin owned a similar Darne slug gun that was a much higher grade. He used his for sea ducks, and had a detachable claw mount scope mount made up here it the states to mount a 4X scope. He used the gun setup in this fashion to take deer and pigs. After Wes died, his gun came to live in Minnesota, and the owner made contact with me, but we haven't had a chance to get together with the gun.
I assumed that regulating a slug gun would be about like regulating a double rifle, but, the maker told me it was pretty easy in comparison. I took him at his word on it.

Best,
Ted
Amarillo Mike and I are the only posters on this thread that seem to realize that a pattern .9" to the left or right of center to infinity is as good or better than a pair of patterns that converge at only one range and then divert in opposite directions. My vote is that the "infinity" pattern is better.
Reality often gets in the way of theory, even good theory...

Best,
Ted
Most of differences expressed here are semantic. You don't get common points of impact with a side by side shot with typical gun mount -- out to infinity or otherwise -- without barrel convergence.

"Theoretically" ... if the load is perfect for the gun's barrel convergence, the barrels are perfectly parallel to the "line of aim" when the shot leaves the muzzle, and the pattern centers are delivered to virtually the same point at all distances, without crossing. Patterns shot with a lighter load cross at some distance; with a heavier load, the pattern centers never coincide, and divergence increases with distance.

As noted before, lots of factors can muddy actual results. The above assumes consistent velocity. It also seems to me that even cast could affect how much each barrel of a side by side moves before the shot exits the muzzles.

Jay
Originally Posted By: eightbore
....the only posters on this thread that seem to realize that a pattern .9" to the left or right of center to infinity is as good or better than a pair of patterns that converge at only one range and then divert in opposite directions. My vote is that the "infinity" pattern is better.



I wonder how the center line of the bores of a side by side shotgun be set to ensure that the patterns of both barrels fly parallel to each other.
Quite simple to make from new , but would look ugly and rather like a big bore double rifle .You will also need extra wide ribs that will add to the weight . I feel a point some seem to have missed is that with a shot gun you shoot a spread of shot where you hope your bird is, you are not aiming at a sitting target so it is a matter of learning where you gun shoots and giving lead accordingly .
A quick calculation suggests that the muzzles are about 1 1/2" apart, or 3/4" to each side from the aiming line when the shot leaves the muzzle
Chuck for centerlines you get 1/2 of each muzzle diameter plus both of the wall thicknesses of the barrels at the muzzle.

So (1/2 x .729) + (1/2 x .729) + (2 x .040) = .809"

Your calculation was too quick grin
Mike,
I think you've been inhalin' too much Britanny poo air. I did say "...when the shot leaves the muzzle". In order for an .011" convergence barrel set to get a barrel pointed at the target, it has to move laterally. That movement only has to be about 3/10ths of an inch if it pivots from the butt of a 50" long gun. 3/10ths plus half your .8-- is about 3/4" or thereabouts, apart from the centerline (aiming line), or 1 1/2" apart from the other barrel when that barrel is fired and the shot leaves its muzzle.

Mike is right, Chuck is covering for his bad arithmetic. The truth is that double shotgun barrels are not straight, they are somewhat bent when being soldered into place. Parallel patterns are created by bent barrels. The Brits figured that out decades or centuries ago. Do you fellows really think that tubes that are a defined distance apart at the breech and touch at the muzzles all shoot exactly converging patterns without bending? They are bent.
Bill, when you look down the bores of the barrels you can see concentric rings. This is true with rifle barrels as well as shotgun barrels. If the barrel is not perfectly straight the rings will not be concentric. Rings in a bent barrel look closer together on the "inside of the bend" and farther apart on the "outside of the bend". Many people don't know how to look for this, but it is easy to see once you know. I cannot speak for anybody else's, but none of my doubles exhibit the non-concentric rings that would indicate a non-straight barrel. It would take pretty severe bends to get rid of the difference in the width of the centerlines from the breech to the muzzle. What you are saying is that the barrels converge for a ways and then bend and are parallel to each other the rest of the way to the muzzles, I think. A bend like that could be very easily seen by looking at the rings, IMO.

I've got a set of Fox barrels in my shop right now from which I removed the ribs. It is easy to see, just by looking at the outsides of the barrels, between the ribs, that they are not bent to become parallel.

All my best, SRH
Well I can assure you of one thing I have never owned or even seen a double in which the bbls were bent to the extent they would become parallel at the muzzles. Hey man i could see that at a glance & I "AIN'T" ever seen it. After seeing the specs in the L C Smith plans & specs book I checked seeral of my Lefevers & they measured extremely close to those Smith specs & no they WERE NOT BENT at the muzzles. I measured their OD's & the width across them at increments & they increased in width at about that .011" per inch just as the Smith specs were stated.
The old timers are said to have straightened bbls by looking through the bores at a line such as a in a window between the panes. It doesn't take a lot of practice to be be able to do this with good accuracy. I have so looked down several bbls * have never looked at one with a rainbow shape or on which the muzzle ends of them had a distinct curve.
That bit about the muzzles being parallel is just FLAT OUT WRONG, please nobody believe that Crap.
the barrels move from time of ignition to the shot leaving the muzzle, if they didn't they would all cross fire by 15"-16" at 40 yds.
Chuck I did misunderstand the point you were making.

But how do you know the barrel axis is pointed exactly at the POI at the instant the shot leaves the muzzle. If firing the right barrel the shot has a component of velocity to the right and that right velocity continues all the way to the forty yard target. You would have to know the velocity to the right to backtrack to where the axis of the barrel is when the shot comes out the end. I don't think we know that velocity.

Another way of putting my argument is that if you were looking down on the shooter that barrel starts rotating to the right when the shot starts down the barrel. So it has a large velocity parallel to the original position of the rib axis of the right barrel and a small velocity perpendicular in the horizaontal plane to the rib axis of the right barrel.

I don't think the axis of the right barrel is lined up with the POI at the time the shot exits the barrel. I think it is pointed to the left of the POI at the instant of shot exit.




Best,

Mike

Please see edit in red

NOW I understand why I shot so poorly at skeet today! It WAS the guns fault! Reason enough to search for another shotgun.....
This is a very interesting thread with lots of great info and I wish I could have read it a year ago before buying the YILDIZ. One thing that I found from it that was very consistent - the heavier the load, the more wall-eyed it shot. As the load increased, the right barrel shot further right and the left barrel shot further left.

The eccentric chokes corrected it somewhat - wouldn't they actually be creating barrel convergence in a sense?

And by the way, the 1.75 oz turkey load at 1100 fps does not have heavy recoil at all. Its not in the same league as a Win Supreme 3.5" 12 gauge load. And you usually shoot no more than one per day, and your heart is racing when you do.:)
Whew, glad I don't have to replace my straight bore cleaning devices with bent ones. smile
Mike
It sure took you a long time to find that animated emoticon. But you did find it. So for that I have to give you credit. Good job.

But this other 'shot slinging' stuff...you gotta quantify it to make it plausible. Personally I think its negligible.
I don't have to quantify to make it plausible. And to get the value of that small rightward velocity we would have to do a high speed camera experiment. We could then calculate barrel axis position relative to POI at the time the shot exits the barrel. And I don't think it is anywhere near your number and that it is much closer to mine.

Thanks for the Emoticon!

We have given my shooting student Joe Wood another excuse for missing.
I'll bring the popcorn.

Joe said you were chasing your dogs again. Win anything?
No, nothing.

But we had a good time and the dogs did a good job.
Mike ,I respectfully suggest that you refer to page 32 Vol;1 The Modern Shotgun by Burrard .The author explains that;"The purpose of converging barrels is to correct for the effect of barrel throw to the left or left or right of the centre of gravity of the gun that occurs at the time of discharge."
Hi Roy.

I certainly agree with Burrard. Chuck and I were having a discussion about the angle of the barrel relative to the POI the instant the shot came out of the muzzle. He thinks it is pointed right at the POI. I don't.

Best,

Mike
I would tend to agree with Chuck on this one. I do not believe the "Twisting" of the gun gives the shot any significant amount of a side vector to its velocity, any more than Swinging on the Bird gives a significant effect on the required lead.
Not to deflect from the discussion . . . but if we have to correct for "barrel throw" (muzzle flip?) to the R or L on a sxs, does that not mean we'd have to correct for the same phenomenon--only up or down--on an OU???
I like to refer to this as the "sling-shot" theory. And Larry, a sxs has a verticle component of "sling-shot" as well. Virtually every handheld gun moves before the projectile (s) leave the barrel. Its dramatic in handguns. There are probably hundreds of youtube slow-mo videos of handguns being fired.
Miller you and Chuck are both certainly advocating that the twisting of the gun is enough that it rotates the axis of the barrel from its initial convergence point to the POI axis in the short time it takes the shot to move from the breech to the muzzle. Using Chuck's 1-1/2" and subracting my 0.8" and dividing by two it is about .35" of displacement in the few thousandths of a second it takes the shot to go from breech to muzzle. And the rate of rotation is much higher at the time of shot exit than at the beginning (0).

My theory is the more likely because the rotation of the barrels in those few milliseconds would be less than the .35" you and Chuck are arguing for.

Of course it wouldn't take a very large side vector to make up a convergence (rate?) of .011".
Gents all this theorising is very good but how about some real tests ? Get one of the magazines to set up some experiments and put this thing to bed once and for all.
Originally Posted By: coosa
The left barrel shot 10" to the left at 40 yards, and the right barrel shot 7" to the right. It was only then that I started to get serious learning about barrel regulation of a sxs. I found that its impossible to get a sxs that will shoot all loads with both barrels to the same POI.


That's probably true for cheaply made production guns.

All the W&C Scotts I've owned all shot to point of impact with any load or shot size I've shot through them (with the exception of Federal flight control wads).



Originally Posted By: coosa
I have been thinking for some time that the perfect turkey gun would be a sxs 20 gauge shooting the heavy tungsten shot. With one open barrel for close shots, and one tight barrel for longer shots, every possible shot should be covered.


Upland choking in a turkey gun is stupid nonsense started by some outdoor writer that didn't know his azz from a hole in the ground.
The perfect SxS turkey gun (which I just happen to own) should be 12 ga. and equally tightly choked in each barrel....
As GT Garwood defines it muzzle-flip is a phenomenon that causes a particular gun to shoot lower than other guns with similar rib to barrel axis angles. Recoil causes a gun to shoot higher if the buttstock is lower than the axis of the barrel(s). I have seen some combat rifles set up so the barrel axis goes through that of the buttstock. I assume this is to eliminate muzzle rise during automatic fire.

Garwood said muzzle-flip usually occurred in longer barreled SxS small bores.

Edit in red
Originally Posted By: coosa

Thanks for the welcome! Yes, I am aware of several hunters using tungsten in a .410, and they are as effective as 3.5" 12 gauge guns shooting lead.


Stupid comments like that should not be allowed on the internet.
Originally Posted By: gunman
Gents all this theorising is very good but how about some real tests ? Get one of the magazines to set up some experiments and put this thing to bed once and for all.


Then we would just have to find something else to theorize about.

It is fun to debate Chuck and Miller. But in the process of defending my theory I have become convinced of its correctness.
Good to see Homey Joe back in the fray.

This thread needs more bile.

But methinks the "stupid comment" was mere bait...
The question is not whether the "Amarillo sling" exists, but whether it's significant.
Originally Posted By: Chuck H
The question is not whether the "Amarillo sling" exists, but whether it's significant.


I agree.
Originally Posted By: HomelessjOe
Originally Posted By: coosa

Thanks for the welcome! Yes, I am aware of several hunters using tungsten in a .410, and they are as effective as 3.5" 12 gauge guns shooting lead.


Stupid comments like that should not be allowed on the internet.


Turkey Comander, is that you? I thought I recognized you from the tone of the post! If not, please accept my apology.

These 2 turkeys would disagree with your assessment of the effectiveness of tungsten. But they can't, cause they're dead. smile



And notice those are mature gobblers killed in the spring; not lost baby hens killed in the fall. smile
Originally Posted By: HomelessjOe
Originally Posted By: coosa
The left barrel shot 10" to the left at 40 yards, and the right barrel shot 7" to the right. It was only then that I started to get serious learning about barrel regulation of a sxs. I found that its impossible to get a sxs that will shoot all loads with both barrels to the same POI.


That's probably true for cheaply made production guns.

All the W&C Scotts I've owned all shot to point of impact with any load or shot size I've shot through them (with the exception of Federal flight control wads).



Originally Posted By: coosa
I have been thinking for some time that the perfect turkey gun would be a sxs 20 gauge shooting the heavy tungsten shot. With one open barrel for close shots, and one tight barrel for longer shots, every possible shot should be covered.


Upland choking in a turkey gun is stupid nonsense started by some outdoor writer that didn't know his azz from a hole in the ground.
The perfect SxS turkey gun (which I just happen to own) should be 12 ga. and equally tightly choked in each barrel....


I don't believe physics knows anything about the price of the gun, or whether it is custom or production.

The idea of the "perfect turkey gun" is very much a personal opinion. For me, the whole point of a sxs is to have 2 chokes - one for longer shots and one with an open barrel for closer shots. Gives me a better chance of not missing one that surprises me and gets too close. If you are gonna choke both barrels the same, what's the point of a sxs?
And what happens if you hit a bird at 35 yards with your tight choke and don't kill him ?

Chances are he won't run towards you...

The idea of upland choking and pixey dust sized shot for turkey is about as dumb as shooting deer with a .22 rim-fire.
Originally Posted By: HomelessjOe
And what happens if you hit a bird at 35 yards with your tight choke and don't kill him ?

Chances are he won't run towards you...

The idea of upland choking and pixey dust sized shot for turkey is about as dumb as shooting deer with a .22 rim-fire.


It is you! I haven' talked to you since they threw you off the GON forum, but file this in the "its a small world" category. I joined a club in TN about 20 miles west of Centerville for spring turkey hunting. I killed a turkey the first morning I hunted it, and then never heard a gobble on it again in 5 more mornings, so I didn't rejoin. Anyway, the club president was riding me around and a couple of jakes crossed the road in front of us. He dived out of the truck with his gun, intending to blast one of them, so I stepped out too. They ran down below us, and I had my Alan Sentell trumpet around my neck, so I started talking to them. They answered and were on their way back to the road when a gobbler sounded off on the other club. We forgot the jakes and set up on the gobbler, but couldn't lure him to our side.

After we left, he was impressed with my trumpet and then showed me his - it was one of yours! Turned out you were a member of the club too, and had given him the trumpet. You shoulda taught him how to run it; he wouldn't even try for me. Said he couldn't make a turkey sound with it. Giving him that call was a very nice thing for you to do - my opinion of you went up a lot. He's not somebody that could do a lot for you, so it was just pure generosity on your part.

Oh, btw, I'm usually poorcountrypreacher on turkey forums, but I use coosa sometimes too. It doesn't take so long to type.

Back to the gun - the right barrel has an almost can't miss pattern at 25 yds. I shot it at 22"x28" poster board at 25 yds and there was nowhere on it that a turkey could have had his head or neck and survived. But it still had a 102 hits in a 10" circle at 40 yds, so if I crippled him at 35 with the left barrel, I could still kill him easily with the right.

I killed the 2 in the pic in GA a few days ago. Shot the first one at 27 yds with the right barrel and he hardly flopped. Went to another spot and called in the second one. I had to move the gun when he went behind the only cover and he caught the movement - had to shoot him with the left barrel at 41 yds, and there was nothing visible over a log except his head and a few inches of neck. He flopped all over the place, but he wasn't going anywhere.

Check the thread that has GLS with his little .410 single shot and several turkeys. It is a 40 yard killer every time. I know you wouldn't shoot one past 40 yards, so his little gun would be all you'd need. wink

Just kidding - we won't ever agree on tungsten for turkeys, but I wanted to tell you about seeing the call you gave away. Good luck in your hunting!
Coosa, how come all your dead turkeys have a red and white bulls-eye on them. I've never shot one with that feature...Geo
Originally Posted By: Geo. Newbern
Coosa, how come all your dead turkeys have a red and white bulls-eye on them. I've never shot one with that feature...Geo


Just a little advertising for the call I used to call them in - a Fatal Attraxion made by Stony Brock.
Originally Posted By: HomelessjOe
Originally Posted By: coosa

Thanks for the welcome! Yes, I am aware of several hunters using tungsten in a .410, and they are as effective as 3.5" 12 gauge guns shooting lead.


Stupid comments like that should not be allowed on the internet.

Steve,you've just met the anti-tungsten shot turkey meister contigency of the forum, rumored to be president of the Earth is Flat Society. Without a doubt, tungsten 9s out of a 20 gauge are as effective as any load of lead #4's shot out of an SBE. To argue otherwise is not stupid, just not based on reality or fact. Not stupid, just militantly ignorant. If stupid is allowed on the net, it is only fair that militantly ignorant is allowed. Stupidity is incurable; militant ignorance takes a lot of time and might as well be considered incurable, but there's always hope. I won't go as far as saying tungsten makes a .410 as effective a turkey gun as lead in an SBE, but I don't consider your remark stupid. Tungsten 9s make a .410 a legit 40 yard gun, but hands down, a 20 with TSS9s is another story as we both know. jOe, hope your season was a good one. One day you will come under Pixie Dust's spell. It already has your attention. wink Gil
Gil - I've seen your .410 patterns, and some Hal has shot too. They have way over 100 hits at 40 in the 10" circle.

The SBE in the pic in my other thread with a Pure Gold choke will consistently give me 70 something hits at 40 with #4 lead. With a Kicks choke, it would go 110-115.

I believe your gun will beat those numbers very consistently.

My 20 with tungsten will blow away any 12 gauge lead load to the point that it is no contest and wouldn't even be a fair comparison.

Good hunting to all!
Originally Posted By: coosa
Gil - I've seen your .410 patterns, and some Hal has shot too. They have way over 100 hits at 40 in the 10" circle.

The SBE in the pic in my other thread with a Pure Gold choke will consistently give me 70 something hits at 40 with #4 lead. With a Kicks choke, it would go 110-115.

I believe your gun will beat those numbers very consistently.

My 20 with tungsten will blow away any 12 gauge lead load to the point that it is no contest and wouldn't even be a fair comparison.

Ah, the veil of ignorance has been lifted from my eyes! I have had an SBE since 1998 and it has had a lead free diet. Nothing but HTL has left its muzzle. And good hunting, to you as well. Gil
Gil, I took time to look at some more .410 patterns, and maybe I need to qualify my statement. I have never shot a .410 load of tungsten, so going by what you see on the internet can lead to misconceptions. Hal had posted the pics in this thread on another board I frequent:

http://www.gobblernation.com/phpBB3/viewtopic.php?f=16&t=5236

Now those patterns will beat any 12 gauge using #4 shot, and since they penetrate about the same, #4 lead is the fair comparison to #9 ts.

However, I see that not all .410s are getting those numbers, so maybe my original statement should have been something along the lines of, "some guys are shooting .410 patterns that beat any #4 lead pattern from a 3.5" 12 gauge." Qualifying it like that would still be called stupid by Homeless Joe, but maybe you could agree with me a little easier. smile

At any rate, many congrats on your season and your success with the little guns!

A good day to all, and Happy Mothers Day to any mothers who happen to be reading about double guns!
Originally Posted By: GLS
Originally Posted By: HomelessjOe
Originally Posted By: coosa

Thanks for the welcome! Yes, I am aware of several hunters using tungsten in a .410, and they are as effective as 3.5" 12 gauge guns shooting lead.


Stupid comments like that should not be allowed on the internet.

Steve,you've just met the anti-tungsten shot turkey meister contigency of the forum, rumored to be president of the Earth is Flat Society. Without a doubt, tungsten 9s out of a 20 gauge are as effective as any load of lead #4's shot out of an SBE. To argue otherwise is not stupid, just not based on reality or fact. Not stupid, just militantly ignorant. If stupid is allowed on the net, it is only fair that militantly ignorant is allowed. Stupidity is incurable; militant ignorance takes a lot of time and might as well be considered incurable, but there's always hope. I won't go as far as saying tungsten makes a .410 as effective a turkey gun as lead in an SBE, but I don't consider your remark stupid. Tungsten 9s make a .410 a legit 40 yard gun, but hands down, a 20 with TSS9s is another story as we both know. jOe, hope your season was a good one. One day you will come under Pixie Dust's spell. It already has your attention. wink Gil


I'm not "anti-tungsten" I shoot Winchester extended range out of my SBE.
As far as your fairy dust sized shot for turkey I can assure you it will never happen with me.


#9 size shot of any material for turkeys is for total idiots plain and simple.
>>>#9 size shot of any material for turkeys is for total idiots plain and simple.<<<

5 years ago, when folks were first starting to use the heavy tungsten for turkeys, I was pretty skeptical about #9 being big enough for turkeys too. That's the reason I started out using 8s, and have killed a bunch of turkeys with them.

But as dozens and dozens of good hunters have switched to #9, and as test after test has shown it has sufficient penetration power at ridiculous ranges, I finally had to agree that the 9s are overall better than the 8s. You get a denser pattern, so you can make a bigger pattern that still will easily kill the turkey.

Joe, there were a lot of folks listening to your opinions 5 years ago and thinking maybe you were right, but the evidence is so overwhelming against you now that I don't think many are listening anymore.

Doesn't matter to me; shoot whatever you want. Just kill the turkey if you are gonna shoot at him.

And I apologize to all for contributing to this excellent thread getting so far off topic. I thought my experience with the wall-eyed shooting sxs might help somebody understand barrel convergence a little better, and I'll be the first to admit I need to know a lot more about it myself. The extreme of a 5 lb gun and 1.75 oz loads made what is a minor problem in most sxs guns into a major problem in mine. I would think the same effect is likely to occur in any sxs gun, but is greatly exaggerated in mine.

Good hunting to all!
Coosa;
I am not a turkey hunter so have not entered into this portion of the discussion. I have killed a Grand Total of two turkeys in my life, both with a 12 Ga & a 1 3/8oz load of lead 4's. hey both did die Dead, on the spot, neither was extreme range by any means.
I did understand the purpose of your original post & it did very well illustrate the point of the fact the gun moves after pulling the trigger & before the shot exits the muzzle. The heavy shot load at a comparatively low muzzle velocity will give it just a bit more time to move, thus accentuating the problem, as of course will the very light weight gun.
I will also note the problem does also exist in an over/under as well. Their bbls also converge though not to the extent of a SxS. Due to the higher plane of its axis from the point of contact with the shoulder the upper bbl would have a tendency to center its pattern higher than the lower "AND NOT" just by the amount of separation of the bbls, which would be insignificant as far as pattern placement goes.
>>>I will also note the problem does also exist in an over/under as well. Their bbls also converge though not to the extent of a SxS. Due to the higher plane of its axis from the point of contact with the shoulder the upper bbl would have a tendency to center its pattern higher than the lower "AND NOT" just by the amount of separation of the bbls, which would be insignificant as far as pattern placement goes.<<<

Very good post, and I have friends using o/u guns shooting the exact same load I am and they didn't have as much difficulty getting their guns dialed in as I did. Everyone that I have heard about behaved exactly as you predicted, with one barrel shooting higher than the other. Some corrected it by using 2 different loads, and others just remember to aim high or low.

I'm thinking it likely that the only way I will ever get a quality sxs to shoot this load to the POA is to have one specially made for it, and it doesn't look like there is anyone around who would do it.
Watch this....
http://www.youtube.com/watch?v=XBwjFvWa9Jw
I don't need size 9 shot to make a pattern.
Originally Posted By: HomelessjOe
Watch this....
http://www.youtube.com/watch?v=XBwjFvWa9Jw
I don't need size 9 shot to make a pattern.



Of course you don't, and I have never implied that you did. Win Extended Range is good stuff and will kill turkeys at 40 and even 50 yds all day. I killed them with #4 lead for many years.

But the tungsten "kill" patterns can be made much larger than the patterns you are getting, and that's the direction I like to go. Like you said in the other thread, Commando style hunting you need every advantage you can get.

Sorry again to get OT in the thread. I'm going to just bow out of this one and turn it over to Joe to post whatever he wants. I've already shared about all I know on barrel convergence anyway.

A good day to all!
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