The problem started with the transfer bar. The Colt and the three screw can be "timed" internally. The Colt has two small arms referred to as stirrups that ride on the trigger cam. A well tuned Colt will never have a cylinder line. UNLESS an ignorant person picks up a Colt, flips open the gate...
If your reference to a three screw is the old model, what reference do you use for the middle model Blackhawk? We refer to the ist gen Vaquero and the niddle model Blackhawk as the old models.
1st Gen Blackhawk (3 screw), 2nd Gen Blackhawk (old model), 3rdGen Blackhawk (new model).