To make a long story short a friend last year blew up his .222rem. It happened when he wanted to shoot cast bullets back loaded a lot to replicate something along the lines of a 22 mag rimfire. I won't elaborate on why it was desirable to do this.
Can reduced loads really generate too much pressure because so much more of the surface area of the powder is exposed to the primer flash ? Sounds plausible. Would a slower powder solve the issue ?