The gauge or caliber of a firearm is stamped on the__________

The gauge or caliber of a firearm is stamped on the side of the barrel. This is a standard practice in firearm manufacturing, as it provides essential information about the specific type of ammunition that the firearm is designed to use. By having this information prominently displayed on the barrel, it ensures that users can easily identify the proper ammunition, promoting safer handling and operation of the firearm. This is crucial for avoiding accidents that could arise from using incorrect ammunition, which can lead to malfunction or damage to the firearm.

The other choices would not typically display the gauge or caliber. The inside of the chamber may have some markings, but they are usually not visible without disassembling the firearm. The end of the butt pad and the side of the stock do not conventionally carry this important identifying information, as they serve different functions and are not the standard locations for firearm specifications.