In the “whyizzit” category there are:
-Rifles, pistols and revolvers chambered for .22 cal.
-Rifles and revolvers chambered for .44 mag, and .357 but I’ve never seen a pistol
-Rifles and pistols chambered for .45, but I’ve never seen a revolver
-Same with 9mm, pistol and rifle, but not revolver
Of course there could be occasional exceptions to these, but to my knowledge none of these exceptions have ever been mass marketed.