Ok, I need to jump in here. The 858's as are all Communist guns blessed with oversize chambers. This is not a flaw, it is to insure that all ammo from all of the various countries that made the stuff will fit and fire.
North American ammo is made to SAMII specs and not Combloc specs.
Sorry to the Federal loving guys but Federal brass is one of the softest out there, thats not a bad thing, it actually allows this ammo to be used were more brittle brass could not be, however, even it cannot stretch to accomidate the long chambers of your 858. When you take it back they will tell you again to stop using Federal ammo, there is nothing wrong with your rifle!!
Scott
Dycor Special Services