Jack O'Connor's "The Shotgun Book" (1965) listed standard bore diameter and choke constrictions for Browning, Winchester, and Remington. 12 gauge, as stated above, was .725. Remington and Winchester were both listed as .730.
Brownings of that era also had more constriction for a given choke than did Winchester or Remington. For example, Mod on a Browning 12ga was .024. Win and Rem were .016 and .018 respectively. Also true right down the line for the other gauges (16 and 20) as well. IC in a Browning 16 was .016; .007 and .008 for Winchester and Remington.
Last edited by L. Brown; 07/26/20 05:36 PM.