Looked at the picture, read the article. And don't believe the metal just failed. I know a probably world class gunsmith, who lives in Canada. He has dealt with a lot of rifles that would up with barrels looking like that. He works with centerfire rifles, so the ones he has dealt with had one or another sort of obstruction of the bore, the rounds were reloaded with the wrong powder, the rounds were reloaded with an over charge of powder.
The muzzleloader is built to use smokeless powder. I don't care for that idea, so only use blackpowder. The shooter claims he used the regular load of 43 grains of smokeless powder. That is a healthy load, so I checked some of my references. Loads for the .458 Winchester Magnum range from 49 to 77 grains of powder - this is meant for elephant hunting. The .45-70 is from 43 to 54 grains - this is a round suitable for any North American game. The .38-55 Winchester is 22 to 35 grains - suitable for deer and bear. The .375 Winchester from 32 to 38 grains - also suitable for deer/elk/bear.
I forgot to hunt down the owner's manual for the Savage, so don't know what they recommend as powder, or how much. But if the owner does reloading, it is quite possible he used the wrong powder, and depending on the type of powder, the rifle could have been way overloaded by using the wrong powder by accident. Personally, I prefer using the same powder in all reloading, handgun, rifle, shotgun - Unique is one that can be used adequately in all 3, and there is no danger of mixing powder that way. He could even have loaded a double charge without realizing it - that was frequent during the Civil War, they even found unfired rifles with as many as five loads in them, but the shooter forgot to fire. Bottom line, I think the shooter screwed up someway, but won't admit it.
Some of the old time target shooters used to use smokeless powder in their muzzleloaders, but they didn't use a full charge. Instead they would use just a few grains of smokeless, then a full load of black powder. The small amount of smokeless was used to insure better ignition of the black powder.
"It ain't what you're told, it's what you know." - Granny Weatherwax
Fawkahwe tribal police SWAT Team
Some days, the supply of available curse words is insufficient to meet my demands.
.....Call me a craftsman, artisan, or artistic, and I will accept that. Call me an artist and you will likely get a quite rude comment in return. I am not a @#$%ing artist.