Just my opinion
Much of the Eastern Bloc ammo is laquer coated to prevent rust to the steel/metal case. Ak's have no problem shooting them. Direct inpidgment gas systeems dump hot gas and carbon right into/onto the bore/bolt-carrier. Eventually the heat and contact will cause bits of laquer to get deposited into the chamber/bolt area. These deposits can range from slight with no problems, to extreem, with cases "glued" into a hot breech. Some people eliminate the worry, by using brass. This is just my humble opinion. This is on risk I don't need. There are many vendors of "LC" brass at very reasonable prices. SurplusAmmo.com for instance. I've also started seeing "ATI" ammo on Able Ammo's pages.