In a mission called Doberman, either Sweet or Smoke will ask you to fight a gang war in Grove Street and you will have to buy some weapons in order to start a gang war so they will ask you to go to a Ammunation Shop close by.
complete the "doberman" mission
You must reach a certain level in the game for most stores to be accessible.
Check the in-game map. It is marked with a "handgun" icon. I can tell you that it is located in the center of town.
you have to compleat a mission for sweet where you have to kill a few ballas members then you can enter ammu-nation hope this helped
Leather face does not exist in san Andreas
You unlock Ammu-Nation in Los Santos during the mission Doberman, which is towards the end of your time in Los Santos before you move on to the next city.
you get weapon spawns in your garage in san fiero
Complete all mission
No
I don't think you can.
do R3 missions in a car
no such thing
ask it