Actually I would do more research, I seem to remember threads concerning loose Issy 7.62 ammo problems on the FAL Files. For some reason I beleive it had to do with loose ammo that has been sitting around on the desert floor after being bounced around on then ran over by a half-track. The combanation of time, heat, distortion, and tumbleing clean to resell gave some problems to folks on the FAL files. As I remember they were serious problems.
I know this has been hashed out before, but I also wouldnt trust a 65k cup pressure round in a rifle intended for 45k cup. Never mind the questionable Spanish metalurugy. Have you headspaced that old Mauser?