I would first try shooting it out with a trickle of 4Fg. Easiest to try, and less messy.
1. take off vent liner, use your primer to put about 10 gr. of 4Fg. in. If jag is seated, use your pick or small enough screwdriver to push/pry it up enuff for the powder.
2. Replace liner
3. Seat the jag lightly on the powder. If it is a portion up the barrel, and won't budge, then move on to one of the other options listed in above posts.
3. Fill a cardboard box with rags or foam.
4. Shoot into the short side of the box, from a fairly close distance, but not against. Ensure a clear shooting lane behind the box. Could pass thru, depending on foam or rags, flop out or ricochet.
It will clear it, PLUS save your jag. Much better than losing it in the brush or buried in a target backing. And I will not say which one I know firsthand.