I've wondered when this would happen. I was seating a round in a case that I had expanded and when the bullet pushed in, the case bound up in the sliding guide like the popular concrete anchor. I tried withdrawing the ram first gently, then with increasing force trying slow pulls and also tapping action. Suddenly the guts came flying out and the seating plug flew into the concrete wall next to the press denting the previously circular mouth. To add insult to injury, the tiny hole where the spring clip poked through is now an oval. I have some flaring punches, but I doubt I will be able to return the seating plug mouth to a precise circle. The tiny hole in the seating body will never be the same. The spare spring clip no longer retains the sliding guide. It's a mess.
I've had great luck with RCBS supporting their dies that go amiss, but no experience with Hornady. I will try contacting them in the morning, but for the moment, my reloading is at a stand still and I just booked Tuesday and Wednesday off due to perfect weather conditions for range work wouldn't you know.
Talk about bad luck.
I have a .45 ACP die set in the cabinet. Anyone ever have any luck improvising that for 450b? It's late and I'm weary. Will give it a try tomorrow morning.
Hoot