I believe all the CEB, Cutting Edge Bullets, Safari Solids are Brass........ the handgun solids are copper, and there is no such thing as CEB cast anything...... Some of the smaller caliber solids, such as .308 and I believe 6.5, I have some .224 caliber, all those are Copper.
Cast, hard or otherwise would not be suitable for elephant in my opinion, of course I am not up to date on the latest greatest cast, but regardless of Lead cast will flow, deform, and this is not good for deptho of penetration, nor straight line penetration.......
In 2002 I was in Zimbabwe and shooting elephant with 458 Lott (before good modern solids I used a Round Nose 500 gr Barnes, and while I got the elephant, it just was not impressive at all). I also had a Marlin Guide gun in 45/70, and this was a time before good modern bullets for 45/70 as well, I was shooting a 420 Cast Performance at 1920 fps. I had taken a buffalo with it, and I did indeed have some bullet performance issues that nearly caused an issue with the buffalo.
After we had the elephant down, taken with 458 Lott, my PH really liked the little guide gun, so after the head was removed we conducted a test with a side brain shot on the elephant head with the 45/70 and the 420 Cast Performance bullet at 10 yards. The tag says elephant skull, that is not exactly right, as it was the entire head intact. On a side brain, the bullet sheared off the cast meplat, and it turned into a pointy bullet, the bullet did manage to reach the brain, but was found only about 1 inch beyond the brain cavity far side......... This is absolutely not suitable. Cast Performance bullets are known for their hardness I believe...... On other Cast Performance bullets I also found similar behavior anytime bone was involved, the meplat just sheared off basically..........
This is covered in the 8 Factors of Solid Terminal Penetration under #3 Construction and Materials, although Cast or lead is not considered, it would fall under this category of Factors.
In todays world, even with Older Obsolete Cartridges, you do not have to use any Cast or any lead anymore, there is just no reason to do so. 20+ years ago in some cartridges, that might have been the only choice. But today, even if a bullet was not available for some really obscure caliber, you can have them made easy enough.......... If I was in that situation, I would call up Dan at CEB and ask for a specialty bullet in the #13 Solid profile, easy enough. I am sure the same would be available from some other manufactures as well. I recently had a desire for a particular solid in one of the smaller calibers, that was not commonly available, touched base with Dan, and in a few weeks I had 1000 of them.........