List one sign that a firearm may be malfunctioning.

A firearm may be malfunctioning if it exhibits a failure to fire or produces strange noises when attempting to fire. These signs indicate that there might be an issue with the ammunition, firing mechanism, or other internal components of the firearm. A failure to fire can occur due to a variety of reasons such as a misfire, a blockage in the chamber, or a problem with the trigger mechanism. Strange noises might suggest that there is excessive wear or damage to the internal parts, which could affect the firearm's operation and safety.

In contrast, a shiny barrel may simply indicate that the firearm has been well-maintained or recently cleaned, not necessarily pointing to any malfunction. A heavier feeling could be due to external factors such as additional attachments or modifications made to the firearm rather than suggesting any functional issue. Lastly, an engaged safety mechanism is a normal function designed to prevent accidental discharge, and it doesn’t indicate a malfunction; instead, it ensures safety until the shooter is ready to fire.