I think we've established that Glocks and S&W's Sigma are pretty much the same gun.... so with that in mind, go take a look at Smith & Wesson's 2005 catalog. It can be down-loaded
here.
You'll notice that it gets the same code for it's trigger type as the rest of S&W's "DAO" guns; "AD".
The code for a single-action is "AS".
The code for single/double action is "A2"
And the code "AT" is for "Traditional Double action".
Also, if you'll go have a look on page 9 of the Sigma owner's manual, found
here, you'll find the following list of terms and definitions:
AMMUNITION - RIMFIRE - Ammunition which contains the
primer material in the rim. Among the most common rimfire
handgun cartridges are the .22 Short, .22 Long, .22 LR, and
.22 Magnum.
CALIBER - The diameter of a bullet, designated in hundredths or
thousandths of an inch (.357) or in millimeters (9mm).
DECOCK - The process by which the hammer or striker is safely
lowered.
DOUBLE ACTION - A firing action where a single pull of the trigger
draws the hammer or striker to the rear then releases it, firing
the handgun.
DOUBLE ACTION ONLY - A firearm that can only be fired in
double action (cannot be fired in single action).
PISTOL - A handgun that contains multiple cartridges in a magazine.
REVOLVER - A handgun that contains multiple cartridges in a
cylinder that revolves at the rear of the barrel.
SINGLE ACTION - A firing action where the hammer or striker is
released from the cocked position by pulling the trigger.
TRADITIONAL DOUBLE ACTION - A firearm that can be fired
either in double action or single action.
Remember that Smith & Wesson has been around a pretty good while, and didn't need to come up with a cutesy-assed term for how their gun worked, as a marketing ploy, like ol' Gaston did when he introduced
his polymer gun, some 20+ years ago. ( I figure Glock saw the reception the VP-70 got, and knew he was going to have to present his gun as being something "different", in order to have any chance at all. )
And Graystar..... I never miss the forest for the trees.
I'm the kind that likes to climb right up in the middle of those trees, see how they're put together, how they "work", and how they are the same or different from the others around them, so I'll know exactly what kind of forest I'm in.
J.C.