Since the Standard for 12ga is .729", with +.003" @ .732 this is really within tolerance of normal, I wouldn't even call it an overbore. Several of my early Lefevers have larger bores than this & quite possibly were bored for brass shells. These should work fine with paper or plastic (wads &/or cases) as long as the chokes aren't messed up.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra