"The Rigby is an ejector rifle. There's no switch on the forend, so I assume it's not a selective ejector. I would assume that a selective ejector would enhance the value of the gun. But, I'm not sure."

Wes

Remove the forend.

Approximately 2/3 the way along the forend Iron from the knuckle there should be a nut, most often square about 3/16 across flats.

If you undo this nut about 1- 1 1/2 turns (depending on its initial set), then this will turn off the ejectors, it acts to remove the tension from the ejector spring. Do it back up to re-engage them. DO NOT OVER TIGHTEN THIS NUT.

Best Wishes