I guess it depends on your prescription in the bifocal. My close sight is too poor to see anything past the muzzle. The long-range part of the lense gives me a sharp front sight, and sharp target. Nice! - the rear is fuzzy of course, but if I streeeeetch things a bit and try the holed tape on the lense, the rear sight as well should be sharp.
My first set of glasses had progressive lenses. They are an abomination for seeing anything your nose isn't pointed at - and since it isn't pointed at your sights you can't see DICK! You normally sight through the top left part of the right lense (right handed) when aiming. With long-range standard lenses or bifocals, this area is in focus for you - with progressives it's someone else's prescription, not yours.
Yes - I am going to try the black tape procedure of sight correction. It works - I know it does - just one of those things I haven't tryed yet - but yes - I know it works without even trying it - yet - it has to - common sense says it will.