Ok Tex, first you need to have a working knowledge of a S&W revolver internal parts and lockworks. If you remove your sideplate and slowly work the action ( unloaded of course, no ammo present ) you will see the top of the trigger lift up on a lever attached to the hammer ( this is the double action sear ) as it lifts the hammer begins to move back, at a certain point, about 3/4 of the way through, the lower portion of the trigger comes in contact with the bottom of the hammer and completes the lifting until the hammer releases. At the same time this is happening the hand, attached to the trigger is turning the cylinder until it locks in place before the hammer falls. At least it should, thats what we call timing. On a S&W 8 shot the cylinder locks way before the hammer drops. This is what I took advantage of.
here is a link to a good picture, not an 8 shot but a J frame. but it shows the relationship and the picture is very clear.
http://www.snubnose.info/docs/lockwork.htmNote the sear engagement hooks relationship to the DA sear. Now look at what they're pointing to as the single action sear, the arrow is in the wrong place as the SA sear is the fine notch slightly above it. Visualize the trigger movement and what the red arrow is pointing to, will start moving toward the void below the engagement hooks, at the bottom of the void you see a ledge, this ledge would normally engage the SA sear and complete the movement of the hammer. This is what I removed. So now as the transition begins and the engagement hooks lift on the DA sear there is nothing to complete the transition and the hammer falls before reaching it's full arc.
Downside, you cannot lighten the mainspring as much as you could with full movement of the hammer. Also you cannot stage the trigger, where normally you can pull the trigger until it starts the transition and pause as the cylinder indexes for a final press. It's going to be a surprise everytime. It is very fast, and the single action is still there for precise shots.
Remember!! This will not work on a 6 shot revolver, I don't think it will work on a 7 shot, the hammer will fall before the cylinder indexes to the barrel, it may not fire or worse, FIRE WHEN THE CYLINDER IS SLIGHTLY OFF AND BLOW UP.!!!!!!!
Please respond to see if I was clear enough.
M25