It's not an obstruction. It's a chamber explosion.
We have seen a few of these recently, and others on other boards have mentioned intentional tests to reproduce this sort of thing with double charges of either shot or powder. The pressure never gets high enough to grenade the chamber like we see here.
I have a theory. How about a defective primer?
Suppose the primer provides a small spark, not the powder saturating flame it's supposed to. I've heard of 'detonation' effects in rifles when the powder isn't ignited correctly, and then it all burns at once when a critical temperature is finally reached.
Could this be what is happening? I'm aware of a DT-10 that was chamber blown with factory shells... perhaps primer manufacture is to blame?
