A nice sporterizing job, I would be concerned about how it was converted to 7.62x39. The barrel certainly looks like military contour, which means either 7x57 rebored to 7.62 or perhaps the 7.65x53 Argentine, which would be the correct bore diameter. In either case, the chamber would be too large in base diameter and length to rechamber to the 7.62x39 case. Since the contour of the barrel indicates it was not set back, the only way to get the correct chambering would be to bore out the original breech and install an insert, then cut the new chamber. Some ex-military rifles have been converted this way, with mixed results. If you inspect the barrel breech with the bolt removed, the insert will show up as a ring around the chamber, also if you see a long leade in front of the chamber before the start of the rifling. If the conversion was done with an insert, the only possible problem would be the insert loosening and coming out. As long as it's secure, the rifle should be safe to shoot, the US Navy converted many M1 Garands that way to use the 7.62x51 NATO cartridge when that became the standard US round.