With a well-placed headshot, the Revolver can be an effective firearm. Once you've picked up a better weapon, though, you'll probably holster it until your other ammunition runs low and you need to use it as a last resort. When that time comes, switch to the Antipersonnel or Armor-Piercing rounds for maximum effectiveness.
Your first opportunity to pick up this weapon will be from inside the baby carriage during the Welcome to Rapture chapter.
Ammunition
Pistol Rounds
These .38 caliber bullets are a reliable way to deal moderate damage to almost anything.
This ammunition has a carry capacity of 48 and a load capacity of 6 or 24 (with clip upgrade).
Armor-Piercing Pistol Rounds
These .38 caliber bullets are particularly effective against metal or armored targets, like turrets, security bots, or all variations of the Big Daddy.
This ammunition has a carry capacity of 24 and a load capacity of 6 or 24 (with clip upgrade).
Antipersonnel Pistol Rounds
These .38 caliber bullets are specifically designed to neutralize non-armored targets like Splicers.
This ammunition has a carry capacity of 24 and a load capacity of 6 or 24 (with clip upgrade).
Upgrades
Pistol Clip Size
An auto-loading clip effectively quadruples the clip size of the pistol. And that it does - from 6 to 24 bullets. I have no idea how they expect you to use a clip on a revolver, though.
Pistol Damage Increase
An ammunition accelerator increases the damage done by the pistol. Don't bother with this upgrade until there's nothing better to take.