It is semi-auto with a single action only trigger, such that you cannot pull the trigger without the hammer cocked first. It is the same system as a 1911, for example.

Single action only. You have to have the hammer cocked first. After firing the first round, you can continue to fire by pulling the trigger.

It is single action, but not a cowboy gun.

Hi David and welcome. It is a Single Action Only Semi-Auto Pistol meaning the slide must be racked for the first shot and then it will continue to fire with each subsequent pull of the trigger until the magazine is empty. Cheers, stay safe and ejoy!

Hi David, this is a SAO semi-auto pistol. The term SAO is used to describe a weapon that can only be used in a single action mode. Single-action and single-action-only (SAO) guns, like many Sigs, are a type of firearm that requires the shooter to manually c0ck the hammer before firing. This is done by pulling back on it and compressing the mainspring before releasing it, propelling a bullet through the barrel.
With a single-action firearm, your trigger pull only does one thing: it releases the hammer. The sole action required for firing is called a “single-action” or single-action trigger.
Double-action and single-action (DA/SA) guns can be used in double-action or single-action modes.
When firing a DA/SA gun, your first shot will be in double-action mode and have a long, heavy trigger pull. In the subsequent shots, the gun will be in the single-action mode and have a short and light trigger pull.
Stay safe & have a great day!