It's probably unsettling enough to face hundreds of convicted felons each day in a job as a prison guard. Now imagine doing that with a gun that might not work. North Carolina Prison officials say the gun maker Smith and Wesson needs to replace hundreds of guns that have been issued to probation and corrections officers because of problems with the safety mechanisms. None of the weapons have failed in the field. However, in testing one out of four weapons would not fire. So far the state has asked that five hundred guns be replaced but that number may rise to five thousand.