Howdy
It's time for a few photographs.
Here is a photo of the parts from a Second Generation Single Action Army, made in 1973. The parts have not changed much since the Single Action Army was first introduced in 1873, and current production is the same. The photo is a little bit fuzzy, but you can clearly see the various cocking notches cut into the hammer. One arrow is pointing to the tip of the trigger, usually called the Sear. The other arrow is pointing to what is sometimes called the 'safety cock' notch on the hammer. In theory, the idea is that when the hammer is pulled back about 1/8", the tip of the sear will lock itself in the 'safety position' with the firing pin pulled back about 1/8" from any primer that happens to be under it. There is a small overhanging lip on the 'safety cock' notch, that traps the sear, so the trigger cannot be pulled when the hammer is cocked to the 'safety cock' position. In theory.
In actual practice, the sear is very thin, and it does not take much of a blow to shatter it. Or to break off the overhanging lip on the 'safety cock' notch. It has been demonstrated over and over again that a strong blow to the hammer, such as dropping the gun onto the hammer on a hard surface, or accidentally dropping a stirrup onto the hammer of a holstered Colt WILL break off this flimsy safety feature and the gun WILL fire if a live cartridge is under the hammer. It has happened many, many times.
Somebody wanted a Cowboy Action Shooter to list guns that are currently made this way. I can tell you with absolute authority that ALL the SAA clones currently made by Uberti and Pietta in Italy share this same design. They all will fire if dropped on the hammer. There is no transfer bar in any of them. There was one model made by Beretta that did have a transfer bar, but it is no longer in production. And the Colt Cowboy also had a transfer bar, but it is no longer in production either. Some of these guns are imported with a special cylinder pin that has an extra cut out on it, so that the pin can be locked backwards, preventing the hammer from falling all the way. Most of us throw that pin away and replace it with a traditional pin that only has one cut out for the transverse latch. Once the pin has been replaced, these guns will fire just like any other revolver made to the Colt design if dropped on the hammer.
For this reason, we have an ironclad rule in Cowboy Action Shooting. ALL revolvers are only loaded with five rounds, with an empty chamber under the hammer. ALL revolvers, even modern Rugers with a Transfer Bar, just to keep things consistent.
Historically, what happened was revolver manufacturers realized the shortcomings of the old Single Action designs, so around the turn of the Century they started producing revolvers that could be safely carried fully loaded. Most of them employed some sort of rebounding hammer, not a hammer block. Iver Johnson even had an advertising slogan, 'Hammer the Hammer' illustrating a carpenter's hammer striking the hammer of one of their revolvers to demonstrate how safe they were.
Let's jump ahead a bit to Ruger. Early Ruger revolvers were very similar inside to the Colt design. Even though they employed coil springs instead of leaf springs, they still had the unsafe 'safety cock' notch on their hammers. And they were just as unsafe as the old Colts when fully loaded with six rounds. So in the mid 1970s Ruger completely redesigned their single action revolver line to employ a transfer bar. A transfer bar is the exact opposite of a hammer block. If the transfer bar is not in place, the hammer cannot reach the firing pin to strike it. When the hammer is cocked AND the trigger is pulled back, the transfer bar rises to a position where it will be struck by the hammer, and then transfer the hammer blow to the firing pin, discharging the revolver. But normally, the trigger return spring pulls the transfer bar down out of position so if the gun is dropped on the hammer, nothing will happen, other than marring the finish of the gun. For this reason, all Ruger single action revolvers produced since the mid 1970s are completely safe to carry fully loaded with six rounds.
Sorry, I don't have a photo of a transfer bar in position, but next time I take one of my Rugers apart I will take one. In the meantime, here is a photo of a Three Screw Ruger. If it has three screw heads on the side of the frame, it is NOT safe to load with six rounds. ALWAYS only load it with five rounds, and keep an empty chamber under the hammer.
Here is a photo of a modern Transfer Bar equipped Ruger Blackhawk. Notice there are no screws at all, just two pins. These are the guns that have the transfer bar and are safe to load with six rounds.
OK, let's move on to Double Action.
I can't tell you much about Colts or Rugers or Tauruses, but I can show you photos of the inside of a Smith. Modern S&W revolvers actually have two redundant safety mechanisms built in. This photo shows the at rest position of a S&W revolver with the trigger released and all the way forward. The arrow is pointing to nub at the bottom of the hammer and another nub at the top of the Rebound Slide. The Rebound Slide has a very strong coil spring inside it, and when the trigger is released, the spring pushes the slide forward which in turn resets the trigger for the next shot. But the Rebound Slide spring is so strong, that as the Slide moves forward the nub at its top wedges the nub at the bottom of the hammer back, pulling the firing pin back from any primer that may be under the hammer. S&W first employed the Rebound Slide in their Hand Ejector revolvers in 1902, and it has been used ever since.
In the next photo, I am holding the trigger back, in the firing position. The Rebound Slide is all the way back, and the nub on top is clear of the hammer, allowing the revolver to fire. When I release the trigger, the Rebound Slide will return forward, pushing the trigger forward and wedging the hammer back as in the first photo. This single feature is what made the early S&W revolvers with swing out cylinders safe to carry fully loaded.
Here is a photo of the mechanism of a S&W revolver made in 1908. The parts are shaped slightly differently, but the concept is the same. The Rebound Slide forces the hammer back. There was no redundant hammer block in these guns, simply the rebounding hammer.
But eventually S&W decided to make the guns a bit safer. so a pivoting hammer block was introduced. Here is a photo of the side plate and trigger assembly from a 38-44 Heavy Duty made in 1930. The hammer block is a piece of spring steel pinned to the side plate. There is a ramp or wedge built onto the pawl and one arrow is pointing to it. The other arrow is pointing to the bearing surface on the hammer block. As the trigger is pulled, the ramp on the pawl engages the tab on the hammer block, pivoting the block out of the way and allowing the revolver to fire.
The story is, during WWII a sailor was killed when a Victory Model revolver fell to the deck of a destroyer, discharging the revolver. Apparently even with the safety features built in, the pin that the hammer rotates on was deformed or sheared off by the blow, allowing the revolver to fire. So S&W got a directive from the War Department to fix it. They brought in their design staff and over the space of one week came up with the hammer block that has been placed in all S&W revolvers ever since.
The next photo is back to the big 44 in the earlier photos. I have placed the hammer block in position. Notice the Rebound Slide has pushed the hammer back. The Hammer Block rides on the little pin in the side of the Rebound Slide. There is an angular cut in the side plate that the Hammerr Block rides in. As the Rebound Slide pushes the trigger forward, it also causes the Hammer Black to rise up to positively block the hammer from moving forward far enough for the firing pin to strike a primer, even if the hammer pivot pin should shear off. That is the redundant safety system inside all modern S&W revolvers.
That's pretty much it in a nutshell, why the old Single Action revolvers were unsafe with a live round under the hammer, what Ruger's solution was, and what one major Double Action revolver manufacturer's solution was.
Yes, the old spur trigger S&W revolvers, as well as all the Tip Ups and Top Breaks would also fire if the hammer was struck hard enough. Some did have a 'safety cock' notch on the hammer, but it could not be trusted.
Besides, nothing wrong with seeking knowledge on what you don't understand.
