Actually MH, that's exactly how it was when it started in the early '70s. That lasted for several years then they decided you could use a conical or saboted bullet. Now just last year you were permitted to use a peep type sight. But we still have a week long 'early ml season' where you can use a scoped inline or caplock ml.
The requirement for both season is that the rifle must be larger than .44 cal.