It is common in older doubles of most makes to find oversize bores. I personally believe this was from the popularity of brass shells during this era. Due to thinner side walls brass shells required larger wads. Guns ordered for their use had oversize bores. Chamber dimensions were normally set for paper shells. There were exceptions however with some undersize chambers & brass hulls for use with standard bores & wads.

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