I believe the BL series ran from BL1 thru BL4. I hunted for several years with a BL-2S which was equipped with the hinged speed trigger. I never had any problems with the trigger and it was easy to select either barrel by moving the trigger finger up or down with no repositioning of the hand. Others that tried my gun didn't fair so well, often moving the trigger finger to the center pivot point resulting in no "bang bang".

Dodging lions and wasting time.....