Since I switched to using worms, I have come to detest and belittle jags.
Jags require fabric of a particular size and thickness. It is quite possible to get a jag stuck. The fabric does a fairly lousy job of cleaning the grooves.
Worms can be used with fabric, tow, unraveled twine, a birdsnest of weed fibers, cornhusks, or whatever is handy, are quite unlikely to get stuck, and the fibers of the material used are more likely to get down into the grooves of the rifling. Our forefathers know what they were doing.