What risk does extra oil and grease inside the barrel pose?

The presence of extra oil and grease inside the barrel primarily creates increased pressure when the bullet is fired. This occurs because the combustion of gunpowder generates gases when the bullet is fired. If there is an excessive amount of oil or grease in the barrel, it can create an additional seal, preventing the gas from escaping properly. This buildup can lead to a dangerous increase in pressure as the bullet travels down the barrel.

Maintaining a clean and properly lubricated barrel is crucial for safe firearm operation. While some lubrication is beneficial for smooth operation, too much can lead to complications such as increased pressure, risk of a barrel obstruction, or other feeding and cycling problems. Understanding this risk is essential for safe firearm handling and ensuring proper functioning during use.

In contrast, the other options reference potential issues that arise from different factors unrelated to oil and grease accumulation in the barrel.