if your talking about the bar that comes up in front of the fire pin that is not a safety. all that does is prevent the gun from going off it its droped on the hammer and the trigger is not pulled.
[edit] Double-action revolvers
On double-action revolvers, there are no external safety devices; a trigger pull will always result in firing (unless the chamber being indexed into battery is empty). In general, the heavy trigger pull required to cock and then fire the weapon prevents accidental discharges from dropping or mishandling the gun. In addition to that fact, most modern double-action revolvers do have an internal safety, either a hammer block or a transfer bar, that prevents firing not originating from a trigger pull (e.g., gun is dropped).
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[edit] Single-action revolvers
Single-action revolvers have no external safeties, and they usually have no internal safeties (such as a hammer block or transfer bar) to render them drop-safe. (Real antiques are in this category; modern replicas may have hammer blocks.) Therefore, carrying them with a loaded chamber under the hammer is not safe. When they are carried (concealed or openly), the hammer should be left down on an empty chamber
unless its some odd gun that nobody carrys or its some junk brand then no they have no safetys.