[ke4yyd]

Below is a quote from another forum. I don't see the logic behind this for a shotgun with barrels about an inch apart at the centers. Any help on this???

"ALL double shotguns are designed to converge their patterns at a certain distance. After that distance the patterns diverge again.

Same is true for double rifles.

The barrels on double guns and rifles are not parallel to each other."

 

[TexasTon]

People spend alot, ALOT of money in buying a gun that both barrels shoot the same POI, and at least two manufacturers have adjustable barrel hangers to assure this is possible.

I know of several, one shooter in particular that went thru 6 425's til he was satisfied that the POI was perfect for both barrels--this was at 40 and 50 yards, and Browning sent them to him til he was satisfied. :roll:

That said, there are alot of guns that don't.

I posted before about a guy I know that waited 28 months to get a high dollar SXS made for him, he got it in and chipped targets for an afternoon til we shot a target box at 16 yards, then on to 40 yards. At 16 yards the shot would take the outside of box off on both sides, at 40 only a rare stray pellet would be on a 48" board. He returned it to Italy and they sent it back as "within specs". The gun would be worthless to me, unless shooting only station 8 skeet targets or pen raised quail, and cost $26K.

After that distance the patterns diverge again.

Now, that isn't quite possible, is it?

I have no idea about a double rifle, but if I had a Lion bearing down on me that puppy better shoot where I aim it :roll: :?

 

[Ulysses]

After that distance the patterns diverge again.

Now, that isn't quite possible, is it?

Sure, it's possible. If the top barrel and bottom barrel converge at say 25 yards, then beyond 25 yards they will be diverging. The farther they go beyond 25 yards, the farther apart they will be.

 

[TexasTon]

patterns diverge

OOOOPS sometimes either my brain doesn't keep up with my eyes, or my eyes outrun my brain :roll: I read it as converge in both places.

 

[Jeff Mull]

KE4YYD,

Shotgun barrels are not parallel because they are thicker at the breech than at the muzzles.

During assembly the barrels are "regulated" to shoot to the same point. They need to be tweeked into alignment so the axis down the bores intersect at a predetermined distance from the muzzle. Regulating barrels is one of the harder parts of making a fine double barreled gun.

The process is similar to aligning a rifle barrel and scope tube. And with a scoped rifle you have the same situation. The are not perfectly together except at one distance. Before that distance they are converging and after it they are diverging.

Note: this oversimplication does not take into account long range rifle ballistics where the bullet rises above the line of site and then falls back into convergence.

Jeff

 

[mike orlen]

With a couple of exceptions (shotguns built on the Remington 32 design, etc.), shotgun barrels are not parallel; they are intended to point at the same spot at a specific range. At a point between 35 and 40 yards, they should converge. Since we are talking about "scatter guns", this difference in point of impact becomes less and less critical as distance increases. A double rifle is an entirely different story. They are built with parallel barrels and impact is intended to remain constant throughout the bullet's flight. There is often some form of adjustment provided in a double rifle; either by adjustable front hanger or by center adjustment. Any attempt to regulate a shotgun to the standards of a rifle has been considered a waste of time by almost all of the best makers in the world. They remain built to converge at a predetermined distance.

 

[Rollin Oswald]

Not all double-barreled shotguns are regulated to shoot to the same point (have the same POI.) Over & under guns designed for trap shooting are regulated to shoot higher with the bottom barrel than with the top barrel. This is done because the bottom barrel with its reduced barrel rise during recoil, is used for the first shot when the target is rising more quickly. If the gun is used for doubles, the second target is rising more slowly and a flatter shooting barrel is desirable.

http://stockfitting.virtualave.net

 

[A5guy]

There is something else to consider when we speak of double rifles. They are regulated to have the same POI at a certain range with a particular load. I ran into this problem when I was getting some Purdey 246 ammo loaded. This is a proprietary round that was only made for the Purdey SxS rifle. Only one load will give accurate results. Thankfully the Purdey Company helped my loader with the receipe. I had 140 empties and loaded ammo goes for $1000 a box of 10 so I had to reload if I wanted to bring back the great little gun. We got the ammo set up to shoot on spot at 65 yards with the proper powder and bullet combination.

 

[Jeff Mull]

Jeez and thought Bizmuth was expensive....

 

[Bill M.]

There is really no logic to "convergence" in the sense that the POI of the barrels must cross at some point. The barrels are 1 inch apart, as you stated. So what if they stay one inch apart at 40 yards. Who will know?

But the barrels do have to be set so that they shoot to the same point of impact. Convergence is just a convenient word, slightly misused for shotguns, to explain that the barrels must be regulated together in some fashion.

 

[Jeff Mull]

Bill,

As the shot charges essentially converge within the range of a foot or so I guess the idea is to not diverge until after the effective range....kinda sorta?

Jeff

 

[JimfromTrafalgar]

Jeff,[and all],
Remember that these things aren't called "scatterguns" for no good reason. Rule of thumb,[unless we're talking some special purpose], is that both barrels should hit the same spot at 40yds. Fewer guns than you think will actually be spot on, however. Minute regulation of the barrels is a tedious and time consuming affair, and drives the price up accordingly. Once again, with shotguns, close is often good enough, the manufacturers know this, and can keep price down by not getting overly picky.
Double rifles are another animal. I won't go into great detail, but the barrels are not parallel. They point slightly inward so as to offset the effects of recoil,[right gets pulled to the right, left to the left], and accuracy depends on regulation, load recoil, and the strength of the shooter. When sighting in, or developing the proper load for a double rifle, one does not clamp it in a vice or embed it in sandbags, as is commonly done with smaller bore bolt actions and such. This is done standing, with one elbow on a rest, to allow for the recoil factor.
Jim