Why do SxS's have to be "regulated"?

[Bud Tugly]

I've heard many times that the two barrels of quality SxS's are carefully aligned so they shoot to the exact same point of aim at 40 yards or so. I don't get the reasoning behind this.

Wouldn't it be better to just make the two tubes as close to parallel as possible? Sure, the right barrel would shoot an inch (at most) to the right of the left barrel, but would that amount really matter with a shotgun? Might be an issue when shooting slugs, but most SxS guns aren't really intended for slug shooting.

I realize that having the two barrels misaligned so they shoot a foot or more apart would be a very bad thing, but I don't get the logic of "regulating" the barrels.

 

[Jim Watson]

If they were built parallel, they would shoot far apart. Recoil begins before the shot is out of the barrel, so the right barrel swings the gun right, the left barrel swings the gun left. The barrels are installed with convergence from breech to muzzle to bring the patterns together. I doubt any but the very finest of shotguns are regulated like a double rifle, though. They just jig them up and solder them together as indicated by design and experience. You can see the difference in pattern centers when the NRA tests a double gun.

 

[oneounceload]

I realize that having the two barrels misaligned so they shoot a foot or more apart would be a very bad thing, but I don't get the logic of "regulating" the barrels.

That's exactly why they regulate them; otherwise at 40 yards, they would be very far apart. They also regulate them vertically as well, to ensure there isn't a major discrepancy top to bottom

 

[ArmedBear]

They don't need to be regulated.

Try a Baikal.

 

[Virginian]

Actually, when they are regulated, the important last several inches of the bores are very close to parallel, if not truly parallel, in order to put the patterns there. They have to be - pure physics. I don't know how many patterns they shoot, and how close they check them, but I would guess center of patterns within one inch at 40 yards, as you noted, is plenty close enough.

 

[ArmedBear]

Actually, when they are regulated, the important last several inches of the bores are very close to parallel, if not truly parallel, in order to put the patterns there. They have to be - pure physics.

Unfortunately not -- or at least "close" isn't the same as "truly", nor is it close enough to be left alone.

Were that true, the Gold Label would be wildly successful, and would retail for $1500.

 

[Bud Tugly]

So the regulating of the barrels is basically done to compensate for the recoil since the barrels are slightly off-center? Wouldn't that mean that the point of impact would be different with high power shells compared to low power since the recoil force would be greater? And also for a very strong person with a firm grip compared to a weak person gripping the forend lightly?

The whole idea of regulation in SxS's sounds more like an art form than a science IMO.

 

[Virginian]

The regulation is necessary because the barrels are much thicker at the chamber end; the outside diameter is much larger because of the pressure and the chamber, and you do not want a SxS as wide between the bores at the muzzle as it is at the breech. And, if they just touched at both ends the charges would cross way short of 40 yards.
Armed Bear, I just don't get your comment relative to the quote from my post.