In the year 2000 Beretta introduced the 12-gauge Optima Bore barrel design into some of our competition shotguns. This new barrel utilized a larger internal bore dimension known to some as “back-boring” and required a new choke tube design to give the proper constrictions. The Optima barrels can be identified by locating the letters “OB” stamped next to the barrel gauge stamp. Barrels marked with the “OB” stamp will use the Optima-Choke system. This design features a longer internal transition taper into the choke constriction, making the overall length of this tube longer than the original Mobilchoke tube.
Barrels that use the Optima-Choke will typically be marked OB immediately adjacent to the gauge marking.
Optima-Choke choke tubes will be marked Optima-Choke.
The start of the threaded portion of the Optima-Choke tube is located a nominal 50.78 mm (2.00 inch) from the breech end of the choke tube.
The length of the threaded portion is a nominal 15.9 mm (.625 inch).
The major diameter of the choke tube thread is 20 mm (.787 inch).
At this time the Optima-Bore/Optima-Choke system is typically used on competition 391 series semi-automatic, 680 series over and under shotguns and Teknys Gold series only in the 391 Urika2 field guns.
Important Note: The Optima-Choke choke tubes are not interchangeable nor usable with barrels designed for the Optima-Choke HP system. Use of Optima-Choke choke tubes in barrels designed for use with Optima-Choke HP tubes may result in catastrophic damage to your barrel and personal injury or death to the shooter or persons in the immediate vicinity!