Hello, I recently converted my Winchester Ranger 120 into a 1300 Defender. I located a barrel that was sold as a slug barrel with a smooth bore. It was sold as a 20" barrel. I measured from the breech face to the end of the barrel and it is just shy of 20". It has open rifle style sights and fixed choke. On the magazine collar it is marked "12" and where the choke mark goes there is an indented triangle. Does anyone know what choke this barrel may be? Thank you for your help.