Youre in the mountain backcountry. Maybe bowhunting or fishing. You're carrying a Glock. When crossing a stream you take a dunking and your pistol is wet or covered in mud.
What is the minimum gear/supplies/spare parts that you would carry in your pack to insure your pistol will go Bang if you need it?
Figure it may be anywhere from a couple of days to a week before you can get it home. Space & weight carrying capacity is limited, so you want to have what you may need - but nothing in excess. (Unfortunately, you don't have pack horses !)