I have a Sako L-579. It is about 50 years old. Beautiful rifle, superbly accurate. The action is strong. Do you have headspace gauges? Go, no-go, and field? Its a good idea to invest in them. Over time, headspace will gradually increase. Hot, overpressure loads can do this quickly. I don't know if a single overpressure load can do it. Did the case rupture? Where? What does the case look like? Pics would be nice. Some of the other loads he gave you may have been too hot, too, but not enough to vent the gasses.
Excess headspace stretches the case and leads to case separation just ahead of the head. Also, if the guy's brass was not only too hot, but also had the shoulder set back too far, then there was excess headspace even if your bolt and chamber are in spec.
I would check headspace. Any good gunsmith will have those gauges if you don't. It would be cheap peace of mind to verify that the bolt and chamber are still in spec.