What should the user apply to the exterior surfaces after cleaning?

After cleaning the M9 service pistol, applying a light coat of CLP (Cleaner, Lubricant, Preservative) or LSA (Lubricating, Preservative, and Cleaning) is essential for several reasons. These products not only provide lubrication to keep the moving parts functioning smoothly but also offer protection against moisture and corrosive elements that could lead to rust or degradation of the metal surfaces.

Using CLP helps maintain the integrity of the firearm, ensuring that it operates reliably while also simplifying the cleaning process in future uses. A light coat ensures that there is enough lubricant to protect the surfaces without causing excessive buildup, which can attract dirt and debris and potentially impair function.

Other options do not provide the same level of protection or lubrication. For instance, applying a generous coat of grease could lead to excessive accumulation, which may result in malfunctions or difficulty in cycling. Not applying anything at all leaves the metal surfaces vulnerable to corrosion, while using pencil lead is an unconventional and ineffective method that does not meet the necessary lubrication requirements for firearm maintenance. The choice of a light coat of CLP/LSA balances protection and functionality, making it the best practice following cleaning.