Anticipating questions that may arise with regard to the three wildcat cartridges in my list, the .450 C&W, the .505 SRE and the .577 VSRE, I am adding a photo of all three, plus a photo of my .505 SRE rifle.
These cartridges were developed in the late 1960's and early 1970's, when ammunition for classic British big game cartridges seemed to be a thing of the past. The .450 C&W is simply a rimmed version of the .450 Watts, made from .375 H&H rimmed brass. I thought if it as a way to duplicate the .450 NE with modern powders and pressure suitable for a double rifle. It is the cartridge on the left.
The cartridge in the middle was made with the idea of duplicating the .505 Gibbs performance, but this plan was stymied by the fact that the Gibbs is a propriatary cartridge and bullets were not available, so I ended up duplicating the performance of the .500 NE with it. I used 570 grain .500 NE bullets with it. The cartridge case is simply a .460 Weatherby case shortened to 2.500" and necked to accept the .505 bullets.
The cartridge on the right is the .577 VSRE cartridge I mentioned in the text. The case was formed from .577 NE brass, shortened to 2.500", with the rim removed and an extractor groove cut in the base. It easily duplicated .577 NE ballistics, and I consideered it a success, except for the irresistable push produced by the recoil, so it found a new home.
The bullet in front is a Kynoch 570 grain .510" FMJ bullet for the .500 NE, which performed equally as well in the .505 SRE.
The rifle pictured is my .505 SRE, which has accounted for one rhino, three elephants and five buffalo. I consider it a success in every way.