This is the result of some research I just finished on the DA/SA topic as applied to the XD. Some of you guys will probably yawn when reading this as you already know it and have heard it a thousand times. This is for the newer members, that like me, have much to learn.
HISTORICAL MEANING of DA/SA
Originally, in the 1800s, revolvers were classified as either "thumb-cocked" or "trigger-cocked". The pistols could do one or the other, but not both. Eventually, trigger-cocked revolvers fell out of favor. So some ingenious designer decided to create a revolver that would do both types of cocking. This new style of pistol was referred to as "double-action" because they could be cocked two ways.
- Double-action originally meant "it can be cocked two ways."
- Thumb-cocked was replaced with the term "single-action." But single-action used to mean "either thumb-cocked or trigger-cocked, but not both."
- Double-action has come to mean what was referred to as "trigger-cock".
- DAO (Double Action Only): This term, as applied to modern handguns, would have caused our forefathers to scratch their heads. They would have probably rejected the idea as illogical. They would have said it's either double-action or single-action, and you mean "single-action." Then they would have asked "which type of action do you mean? Trigger-cocked or thumb-cocked?"
Source:
http://en.wikipedia.org/wiki/Double_action
THOROUGH DISCUSSION of MODERN DA/SA DESIGNATIONS
To catch up on a discussion of the issue, you may want to take a look at this article. It discusses issues involved with DA/SA and the XD (along with other handguns). It is very helpful - especially for new LAOs who are just jumping into the bureaucratic wrestling match.
http://www.handguninfo.com/Archive/www.Pete-357.com/xddasa.htm
The writer (Pete) mentions that Massad Ayoob considers handguns like XD to be BMDA (Bio-Mechanical Double Action) because the XD feels like a DAO system to the operator, even though it requires pre-cocking using a slide rack.
- Mike