9mm

The 9mm is the most basic weapon in Grand Theft Auto: San Andreas. A lot of gang members will carry this as well as the cops. When you reach Hitman status with this weapon you can wield two of them at once. It holds 17 rounds per clip.

Los Santos
From your house in Ganton, head next door to Sweet's house. Go behind Sweet's and run alongside the wall behind the house. You'll find the pistol in the corner.
 * Ganton - Corner of wall behind house on Grove Street

From your house in Ganton, head east towards the main road that overlooks the ocean in East Beach. Head north from there and take the last left before the road leads out to the countryside. Take the second left after that and at the end of the road, look for a wide opening between the last two houses on the left side of the street. The pistol is at the back of the opening by the wall.
 * Las Colinas - Beside wall in opening between two houses

From your house in Ganton, head east towards the main road that overlooks the ocean in East Beach. Head south from there towards Playa Del Seville and follow the road as it curves west towards the Ocean Docks. Continue following the road until you reach the Santa Maria Beach. On the south side of the beach is a wooden pier with a Ferris wheel. On the west side of the pier is a lifeguard post. The pistol is by the post.
 * Santa Maria Beach - Beside lifeguard post

San Fierro
From your garage in Doherty, head south and take the third right. Head down the alleyway on the right side of the street after the second right turn. When the narrow alleyway opens out slightly, look to the right and you'll find the pistol in the corner.
 * Garcia - Corner of alleyway

Desert
From the Fallow Bridge, cross the bridge and take the second left before you reach the fork in the road. Follow this road until you reach a bridge. Cross the bridge, and immediately after you'll reach the Kincaid Bridge (the railroad tracks). The Colt .45 is located behind the stone support beam on the left side of the road.
 * Tierra Robada - Under railroad tracks stone support beam