I recall that article by Ross and thought, OMG - that's big.

The biggie, here, is if the ctg. will chamber with the oversized ball or bullet. Was it chambered for a paper or brass ctg. Brass, of course, will allow much larger diameter bullets.

In the oval bore, I'd be trying round balls slugtly undersized and cloth patched, maybe - pure lead first - at slightly over 'bore size'. I know it sounds strange and not original, but I also know they work in a number of double and pump guns we've tried them in. They do not sound orthodox, but do have advantages perhaps not thought of. No leading, clean shooting with simple mink oil or neetsfoot oil lube, or melted beeswax with an oil for lube. I'd be concerned of the muzzles expanding with too much bullet diameter and mass exiting, depending on the muzzle thickness (weight), of course.

When round balls were made available (most called them Punkin balls) for any old shotgun they were kept way undersized so they wouldn't damage the muzzle of choked gun. That is why they were so inaccurate, of course. Modern Foster-type hollow based slugs, with 'vanes'/'rifling' on them had those 'soft' raised surfaces so the chokes wouldn't be damamged. Granted, modern full choked shotguns have less 'weight' in the muzzles than the old English guns. Perhaps the modern ones do not need the weight, due to stronger materials? I don't know the answer to that.

I know Ross was concerned, but kept trudging along in testing and came up with the answer for HIS gun- way ovesized bullets.

I would not boldly go where no one (we know) has gone before with MY gun. It would take time and careful loading to find what the gun wants - or it would, if it was mine to test.