The original DAO pistols from the early 90's had short, sweet trigger pulls. Damn near single action. This was because S&W was making a proprietary slide and frame for the DAO models that extended further to the rear, covering the cocked hammer. These pistols can be identified by a round firing pin retainer.

In the late '90s, starting with the TSW rail models, they began using standard frames and slides to save money. These can be idientified by an odd shaped firing pin retainer, the same shape as a safety. The drawback to this is the original 3/4 cocked hammer looked like a cocked pistol with no safety. The lowered the hammer to a 1/2 cock, which looked more presentable. It also gives a slightly longer pull. It is still better than the DA pull on a DA/SA model.

There were also a limited number of compact 9mm's made for a police contract that had full stroke DAO triggers. These had double strike capability.