inspect the other rounds carefull. if the the primers are starting to come bac e instad of a dent then its still got issues . the primer should just have a dent .
I hand load an im at max when the primers have a dent with a ring coming back around the dent .
the barrel being all welded to crap may have shrunk the bore or screwed it up an be causing high pressure . the weld is right abut were the bullet is or in front of it . no way that much welding was done with out affecting the bore.
the gun is making high pressure with the one ammo you need to look the other stuff over really close .