The grand slams are poured in two stages. They are not a cup and core. The innards are molton when applied.They are poured with a harder compound in the base, then, the second stage is poured, They are then swaged to size and shape. I have hundreds of them, and they perform flawlessly. I haven't recovered one of them ever, as they do a complete pass through. The bearing surface is a little different on them than another bullet. You will have to develope a load for them starting from scratch again. IMO, they are as good as a Nosler partition.