Tow rag could be used for cleaning guns, the tow fibres after hackling could also be used for cleaning the bore of a gun. After use for gun cleaning it might be used for kindling a fire.
Tow is the short fibres left over after combing or “hackling” the longer flax fibres called “line”. Flax is a plant that was dried and pulled through a hatchel, like the one below.
These fibres were then made into tow cloth, which, in the 18th century was used to clean gun barrels, and when they were finished, it was put into their fire bag and used for lighting fires. Tow was an inexpensive material and was also used to make work clothes and work frocks.
More Information: http://flaxforsale.com/html/flax_process.html