okay i have verylittle experience with any kind of handgun/revolver i have shot a S&W .40 Sigma twice other the that simi auto wise i have only shot a .22 with revolvers i am a little better i am a fairly good shot with most revolvers i have used. witch isnt many a few .357s and a few .44s...but anyway to my question
a revolver like a ruger new model blackhawk is single action meaning that you have to pull the hammer befor you can pull the trigger
a revolver like the ruger sp101 thats hammer less is duoble action only, this means that you can only fire by pulling the trigger witch cocks and fires just all by only pulling the trigger
a revolver like the gp100 is double action because you can just pull the trigger to shoot or you can cock the hammer manualy and then pull the trigger
so whats it mean when they are talking about simi autos and say DA or DAO?
Some autos...like the 1911, are semi-autos single action...you have to cock the hammer manually for the first shot, then the slide recocks it for subsequent shots.
Some Semi autos are SA and DA, meaning you can either cock the hammer the first shot, or just squeeze the trigger. These types also automatically cock the hammer after the first shot...so the trigger pull is very different for the second and following shots.
Some semi-autos are DAO which means the hammer never stays cocked back...kinda like the hammer bobbed revolver you mentioned.
Some semi-autos are striker fired, like the GLOCKS for example, and don't have a hammer...they use a spring and firing pin...kinda like a bolt action in a rifle.
I hope this clears it up some...I'm sure I missed a few points and others will have more to tell you.