The tungsten cored Grand Slams are still here
A couple of retired Blount Execs who made and used these bullets, bought the rights and are again making them on a small scale. 458's and 416's for sure, and I can see about the .375's. If anyone is serious, P.M. me and I'll pass their contact info along. But without the economies of scale at Speer, these will be quite expensive, per bullet. I don't know just how much, but they did and still do, fill a niche.
When Federal got their hooks into Speer, they didn't want to compete with the Speer African Grand Slams, as they were already putting another premium bullet in their African Ammunition.
The best part, is that as a custom number, you get to specify where you want your crimping cannelure.
I don't have any financial part of this, but I do know who is making them, and can put you in touch. You might also contact ATK ( Speer) customer service, and ask them, for the new contact info, as these guys did buy the rights, and are above board in their dealings. At least that's what I've been told.