Single action means the trigger does not cock the hammer or striker. That's all it means. It entails nothing else.
Double action means the trigger cocks and fires the hammer or striker. That is also all it means.
DA/SA means that you can safely put the trigger forward after chambering a round and then can get a long, hard double action trigger pull when it is time to kill stuff. You could also recock the hammer manually, and then fire like normal. DA/SA triggers are worse than SA triggers.
I prefer DAO(nly) for derringers, DA/SA for revolvers, and SA for automatic pistols.
My derringer, Double Action Only. It's a High Standard DM 101 in .22 Magnum. 2 shots, no hammer cocking:
My favorite revolver is Double Action / Single Action, Smith 686 in .357mag with 6" barrel. You can cock the hammer manually (with your LEFT fucking thumb), or fire it double action which turns the cylinder counter clockwise to be in line with the barrel as it simultaneously cocks the hammer and at the end of the trigger pull it releases the hammer forward. You can also cock the hammer back with your right thumb, but then you also have to shout out, "I AM A FUCKUP!" while doing it.
My favorite automatic pistols are my Colt 1911 and my Browning Hi Power. The 1911 is a Gold Cup with some work done and Colt custom shop parts put on it because my old man handed a guy on the line a $20 back in the 70's. So it's pre-shit safety of the 80's series. The Browning might be older, I forget. I bought that one used a couple years back. I got a silencer on the Browning, but not on the 1911 yet. Sorry about no pics. They're both Single Action. You chamber the first round manually like you do with all semi auto pistols (auto refers to "auto-loading" meaning the mechanism chambers a round itself after you fire the previous one, semi means it doesn't automatically fire that second round immediately after chambering it), the hammer is cocked by this action, and the gun is ready to fire at your press of the trigger. When you press the trigger, the gun fires, cycles, and the hammer is back and ready for you to press the trigger again. The difference between this and Double Action Only guns is that they do not cock the hammer when the slide cycles, you have to manually do that with your trigger pull. That almost always means a terrible trigger pull, but some consider it "safer" because it is harder to fire.
The Colt 1911 Gold Cup
The Browning Hi Power (it is not powerful, I think it's from a bad translation of "high capacity" from that dirty Frenchanese language some Belgians speak. The designer of the 1911 (John Browning) was polishing off this gun's design when he died. The guy that finished the design was Beligian, Dieudonn
é Saive. Considering it was designed across two continents, it served on both sides of WW2, but never makes it into videogames becasue programmers are douchebags. Saive also designed the second most prolific rifle in the world today, the...
FN FAL (Frabrique Nationale - Light Automatic Rifle) LAR in English, FAL in Frenchanese. They're only second in production to the AK-47, and that's only if you consider 20 models of AKMs and AK-74's and AK-101's and RPKs to be "AK-47's". This rifle, like every rifle I have ever fired, is single action. Every rifle and shotgun that I own is single action, semi auto or not. Pump, lever, semi auto, double barrel break-open, they're all single action in this family. Never fired a revolving rifle or a single shot black powder thing. These have been on both sides of wars before as well. It is rumored that God didn't revive Jesus, but that actually Jesus was pissed that he died before the FAL was designed and he came back to life and ginsu kicked the rock off the cave. However, not even Jesus was able to rename the vagina the "not-as-good-as-an-FAL-orifice", the feminist movement was just too powerful.