Could possibly be a burr on the edge of the chamber caused by dry firing, but I've not seen this problem with a No.2 before.
It seems that if an entire case were stuck, inserting a bullet would be difficult and would get stuck itself. Localized burr seems more likely, but only because the bullet will enter the chamber- likely with a small amount of damage. The brass case is hard enough to stop further forward motion.
Thanks for the suggestion ! I took a closer look at the chamber and discovered a small dent in the chamber throat at the 5 o'clock position. Looks like the bullet clears the dent but the case won't . Any suggestions on a quick fix ? Thanks again !