Doing a little research last night with Jean Huon's book, and I found some interesting information on the .303...
First, the guilding metal jacket was adopted for use in 1910, but was used concurrently with cupro-nickel jackets and cupro-nickel washed steel jackets for what appears to be quite a few years. I guess they left their options open.
Secondly, and this is for you, Gyvel, Huon mentions that the .303 was developed based on a cartridge that had been developed by Col. Rubin. That was something I never knew.
Rubin was a prolific cartridge designer, and developed a series of small bore black and smokeless cartridges in the 1870s through the early 1900s, some of which were produced commercially in Europe.
Apparently the British took one of those cartridges as the starting point for the .303, but as I noted below, it's EXTREMELY unlikely that they ever discussed that fact with him.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.