Final answer:
You typically look at the barrel of the shotgun or the ammunition box to determine the gauge and length of the shell for a shotgun, which are crucial for ensuring proper and safe ammunition use.
Step-by-step explanation:
To determine the gauge and length of the shell for a shotgun, you would typically look at the markings on the barrel of the shotgun or on the ammunition box. These markings provide critical information about the size and type of ammunition that is safe and appropriate to use with a particular shotgun. The gauge of a shotgun is a measure of the barrel's internal diameter and is important in determining the size of the shot and shell that will fit. The length of the shell indicates the size of the shotgun shell's 'case' which affects both the load (amount of shot or pellet) and the required chamber size in the shotgun.