[Mr_Leone]

Rarely played GTA SA, beat it once, didn't really go back but I'm thinking of another round. Is the SD pistol a real stealth weapon? Will you not be detected if you fire it? Does it work?

[lil weasel]

SD? You mean Silenced 9mm pistol?
NO, it is unreliable. Sometimes (during missions) it might not be heard other times it is.
Best pistol is the Desert Eagle. OSOK (One Shot One Kill.)

Check out the 2012 Weapons Guide.

[Mr_Leone]

I'm aware the Desert Eagle is a monster! I'm just thinking of playing like a ninja, being stealthy etc.

[CJGroveStreet4Lyfe]

I found SD pistol effective as you CAN be stealthy with it as long as other people aren't too close to hear. Mad dogs mansion is a good example of this.

[lil weasel]

Regretably 'Madd Dogg's mansion' is a mission. Therefore the weapon 'works' because it is required to work. Many missions allow for special activity that will not work otherwise. (An example is the final escape from the Casino Heist where you can glide from the roof to another roof, but you can't do it otherwise.)
I've found that using the Desert Eagle instead of the Silenced Pistol is much more effective when leaving the MD mansion.