A "VERY SIMPLE" look down the barrels of a SxS double will plainly show the barrels "Converging". they are wider apart aat the breech than at the muzzles. If that's not converging then one of us doesn't understand what "Converge means. Also I have taken several sets of barrels, measured their OD's, then measured across their outer diameters, They are "NOT" swamped together, they maintain a steady convergence for their entire length.
Plans & specifications for te L C Smith gun show this convergence to be about .011 per inch of barrel or .330" on a 30 inch barrel. If their axis' were extended in a straight line they would cross between 5 & % 1/2 feet from the muzzle. At 40 yards their axis' would be a bit over 15 inches apart. I measured some of my Lefever barrels & found their convergence to be almost identical. Due to the torques involved in shooting as mentioned above this is"NOT" where the charge actually hits, but this convergence is built-in to compensate
for that torque. Data was listed here for the 12 & 20 gauges but none for the .410.
Stan I highly suspect your problem with your .410 is one of two things. Either the gun is heavy enough in proportion to the shot charge that it is simply not being torqued around, or the barrels were jointed closely enough at the breech & due to the thinness of the muzzles they were given too much convergence at build. A careful measurement of the C/Ls of the bores at breech & muzzles might give some insight on this. I would think it should be less than that for the 12 & 20.
