I just recieved my Polish kit from FAC and it's not in great shape. The hand guard is worn, there are small rust spots everywhere and upon inspection of the barrel, there is a semi-circular cut about 0.5mm into the the top half of the end of barrel most likely from diassembly. The trunnion shows no such cut so I'm not sure how it was cut. Is it still usable? Should I file it down smooth?