Hits on cocktail sized paper plates at 25 yards or closer are entirely possible with 12 or 10 bore round balls from a smoothbore - a left and a right - or even pairs of shots.

IT will take time and experimentation to do that, but it is possible with cylinder bores & 2 sights. It is much more difficult if there is only the front sight. The use of chokes compounds the problems with load development - ie: ball sizes allowing passage through the choked portion of the bore, just as getting double barrels to regulate with single loads that shoot well from BOTH tubes. That in itself can sometimes be hair wrenchingly difficult.

However, once accomplished, it is done.

I once had an English made 12 bore SxS that I shortened the tubes to 26" (or was it 24"?) and worked on developing round ball loads for hunting deer & bears. Here, moose & buffalo (bison) require the use of rifles.

My loads, one with black powder and one with smokeless would keep 4 and once 6 shots in a row, alternating rights and lefts, on a 10"x12" steel plate hanging at 100 meters, shot offhand. I had a scope mounted on a base screwed into the top rib, just for load development.

In those days, open sights would have worked just as well.

I foolishly sold the gun to a fellow who wanted it only for shooting moose from his tree stand. He still uses it, every year, with the smokeless load developing 1,500fps with a .690" ball held in the cupped base of an AA12 trap wad (base removed from the wad & cupping the ball). A load of SA4756.