The double edge sword to me is the profile of old double rifles. You can't use slow powder because the tubes are so thin starting from the fore stock. Fast powder can spike.

Varget and R15 are medium powders that are probably the safest.

Modern barrels are made from Chrome Molybdenum steel that is very strong and highly elastic.

But, here is the reality. Every time a rifle is shot the barrel is strained which work hardens it. The metal fatigue, which is cumulative, reaches a point where it can not contain the pressure and ruptures.

With modern 4130/4140 that's thousands of rounds, with the old low carbon steel, who knows?