I've never heard someone call a shotgun an "old slam fire". That sounds like something a layman would call a shotgun that is capable of slamfiring. Slamfiring in a pump-action is a design oversight, not a feature. That's why most people don't identify a shotgun by it's ability to slamfire.

BTW, slamfiring a pump-action shotgun (like a Model 12) a lot can damage it over time, because the round can fire before the bolt is completely in battery. This can eventually lead to a catastrophic failure, kind of like what happened to you. I don't know if that was the cause, but it's why new pump-actions don't slamfire.

Some things to consider before buying another "old slam fire".