Does anyone know where to find a 18" modified choked barrel for a Wichester 1300 Defender? All I can find are cylinder bore barrels. I have a 1300 Defender and just finished a Shotgun school at the Ga. Public Safety Training Center. I found out that past 15 yards my pattern is something of a mess (3 pellets on target at 25 yards). I need a choked barrel for this weapon. I like the Winchester. Thanks!