[Xringshooter]

Until they split. Even if they split when you fire them, the way they are encased by the cylinder (revolver) or the chamber (semi auto) there is very little chance of hurting the gun or the shooter.

Watch out for nickle plated cases, it appears to me (through many years of shooting and reloading) that they develop splits quicker. It may be that the brass may be a bit thinner to take into account the nickel plating.