Ahh...ok. As others suggested pound away !
To make a long story short, the steel case does not expand as well to seal the case body against the chamber walls ( obturate ) . The result is there is a bit more carbon buildup form gases in the chamber wall
Contrary to popular belief it is not because many steel cases are lacquer coated . This has been discussed to death on the internet
Eventually build up can stick case in chamber
Here is a pic of Wolf 7.62 ( NON lacquer coated BTW ) that actually ejected out of a AR . Ejection became sluggish about 30 rounds before I saw this lying on the ground !
I kept pounding away ( another 200+ rounds ) before it finally stuck a case . Didn't take too much to pop out
I always have a chamber rod with a 44cal brush to make a quick pass in the chamber periodically when shooting the steel case 7.62 and 5.56 . You would be surprised how much crap comes out of the chamber