I did something similar a few years back - forgot the adapter that goes from my range rod threads to the special brass seater jag made for Barnes X bullets. So I just started the bullet, got the jag going down the barrel, and finished the job with the range rod. About then the cell phone rang.

Twenty minutes later I got off the phone and pulled the range rod out of the bore. The recoil, with 150 grains of Pyrodex pellets,almost knocked me off the bench. Downrange 50 yards, I could see the bullet hole and just below it was the perfect outline of that big brass jag where it went through the target sideways. No damage to the gun. Some temporary damage to the shooter.