Please remember that TULA russian crap has very hard primers,I only use high quality surplus nato brass cased ammo in my german weapons.Yes,get all the grease out. You want these weapons dry inside the chamber area. It sounds like its not going into BATTERY. This means,the bolt head is not seating up against the barrel face,hence no FIRE or light primer strikes.Its bouncing back out of battery. I had this happen to a brand new PTR before. Firing pin could be used,but I doubt it. Clean it dry,especially inside the chamber flutes. Drop the hammer on an empty chamber[ofcourse] and check bolt gap with feeler gauges,between the back of bolt head and fron of carrier. Sounds like a new rifle so clean it and get back to me. If the bolt gap is lower than .010,I would send it back to PTR INC. It may have just been dirty inside the area in question. Sometimes a new HK locking piece can bring bolt gap up a little. There are several things it could be,without me seeing it in person. Let us know. It should have fired all those rounds,firing out of battery can be dangerous if it fires this way. Just my exp. not trying to start an argument with the masses.I do have 0ver 10 years exp . with this platform.