Howdy
For $250 I'd say you did very well.
Here are a couple of photos of my Model of 1899 that may help you understand how the rebounding hammer on your Model 1902 works.
This photo represents the condition of the revolver after a shot has been fired. The hammer is all the way down. My finger is holding the trigger back. The part the arrow points to is the rebound lever. Notice there is a space under the front of the rebound lever.
In this photo I have released the trigger. You can see the trigger spring has flexed and rotated the rebound lever slightly clockwise. In doing so, the bump at the top of the rebound lever has rocked the hammer back slightly, enough to withdraw the firing pin into the frame.
This Model 1905 from 1908 incorporates the newer rebound slide design. In this at rest position, the rebound slide spring (you can see it peeking out through the slot in the rebound slide) has shoved the rebound slide all the way forward. In this condition, the bump at the top of the Rebound slide has rocked the hammer back slightly, an arrow indicates the gap between the hammer and the frame. When the hammer is cocked, or the trigger pulled, a strut pinned to the trigger will shove the Rebound Slide back, so that when the hammer falls it will clear that bump, allowing it to fall all the way.
This was the design S&W stayed with for several years. There was no physical hammer block at all in these guns, it was felt that the rebounding hammer was safe enough. Certainly, it was safer than the old Single Action revolvers of the 19th Century. Most of them had a so called 'safety cock' notch on the hammer, so the hammer could be locked back slightly with the firing pin withdrawn into the frame. However the parts in a Single Action revolver are quite thin and fragile. So it was well known that a blow to the hammer with a Single Action revolver would probably cause the gun to discharge.
Here are the parts to a Colt Single Action Army. One arrow points to the so called 'safety cock' notch in the hammer, the other arrow points to the sear. Notice how thin the sear is. If it is seated in the safety cock notch, a strong blow to the hammer will easily shear the sear right off the trigger, and the hammer will go forward and can fire a primer in a cartridge under the hammer. The rebounding hammer on a S&W double action revolver was certainly stronger than that.
At some point, S&W decided the rebounding hammer was not enough to guarantee a discharge in the event of a strong blow to the hammer. The section of the hammer where the rebound slide contacts it could shear if the blow was heavy enough, or the stud the hammer rotates on could even break. So they added a hammer block to the design.
This 38-44 Heavy Duty was made in 1930 and it has a hammer block. The hammer block is the long thin piece sitting in a groove in the side plate.
The hammer block is a piece of spring steel. It is staked in place in its slot in the side plate. The spring action of the hammer block will keep it positioned so that the projection at its top will fit in between the hammer and the frame, preventing the hammer from falling all the way, even if struck. The arrow points to a tab on the hammer block, and the other arrow points to a ramp on the pawl. When the trigger moved, in either single or double action, the ramp on the pawl would act against the tab on the hammer block, depressing the hammer block into its slot in the side plate, and withdrawing it from intervening between the hammer and the frame.
This is the type of hammer block that S&W built into all their revolvers for quite a few years, until the incident that killed the sailor during WWII. An inquiry determined that something had prevented the spring action of the hammer block from acting properly, probably heavy cosmoline inside the action, and the hammer block had gotten stuck in the withdrawn position, allowing something to break inside when the hammer hit the deck, discharging the revolver.
The military demanded rapid corrective action, and S&W quickly came up with a new hammer block design.
This is the new hammer block that S&W came up with. The hammer block rides in a slot in the side plate. The hammer block is a stamped part, and the top is twisted and bent at a right angle. The bent portion fits between the hammer and the frame. A pin was added to the rebound slide. The pin rests in the slanted slot in the hammer block. When the rebound slide moves back, the pin drags the hammer block down in its slot, clearing the hammer to fall all the way. When the trigger is released and the rebound slide springs forward, the hammer block is pushed up again, blocking the hammer from falling all the way. Notice there is a small space between the hammer block and the hammer. The hammer never actually contacts the hammer block, unless there is a failure.
This is the same type of hammer block that S&W still installs in all their revolvers. It is a very proven design. It has been said that the old design was not very positive, relying on the spring action of the hammer block, and that was why it failed. I would add at this point that although the modern hammer block is more positive than the old design, it still relies on a spring for it to function. However the rebound slide spring is a very strong spring, and has proved more reliable over the years than the old design.
