This is embarrassing but here it goes. I fired a few rounds from my new Ruger SR-556 today. I passed a bore snake through it 4 times with no problem. After the 4th pass, a bit of thread from the inside came out so I tied a knot around the snake and snipped off the excess. On the 5th and final pass, the snake got stuck in the barrel. I mean really stuck.
The end of the bore snake is about an inch past the chamber. The rope and first 14" or so of the snake are out of the muzzle.