You say that you normally stock a sxs higher to counter barrel flip. What exactly is barrel flip and why don’t o/u’s suffer from a 90 degree version of it? I searched the archives and couldn’t find any discussion of it.
Barrel flip on a SxS is a slight flexing of the barrels on discharge so as to lower the muzzles very slightly. I never really worried too much about the how or why of it, but it does happen. SxS do shoot lower than O/Us when the same sight picture is used. If you frequently switch between these types of guns as I do, you will definitely notice it. It may well occur in SxSs because most of them are game guns with thin barrels and stocks given to flexing more easily.
The O/U’s bbls don’t flex downward due to the alignment and structure of the barrels reinforcing each other. You know, I don’t have the vaguest idea why O/Us don’t suffer a lateral version of barrel flip, but they don’t. I never really thought about it because it wasn’t a problem. That’s why I’ve never written about it. I guess that the vectors of the recoil don’t have any lateral angle.
There is a tendency of O/Us to shoot the top barrel higher than the bottom barrel, but that’s not barrel flex. That’s due to the higher axis of recoil when the top barrel is fired. This makes the muzzle rise more than when the bottom barrel is fired. In theory this is taken into account at the factory when barrel convergence is set. In fact, it is at least noticeable with fully half the O/Us out there.
For this same reason, the SxS also will have some lateral vestige of this problem. It’s always exacerbated by a combination of cast and a thin, flexible wrist often found on field guns. A right handed shooter using a light weight, thin wristed gun with cast and a heavy load will often find the right barrel shooting to the right. Think about the flex of the stock on recoil and you’ll see that it makes sense. This phenomenon is different from barrel down-flip on the SxS. In both cases the variance of impact can vary with the power and recoil of the load.
With all this stuff going on, it’s amazing that we can hit anything. Of course, the humble gas gun has none of these problems and always shoots straight as a laser. Where is the justice in that?
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)