There is no difference. Cordite = Nitro.

There's black and semi-smokeless (there's no such thing as "smokeless", all "'smokeless" propellants produce particulate yield - smoke - during combustion. The correct term is "'smokeless" which is simply a contraction of "semi-smokeless").

Semi-smokeless propellants are generically referred to as "Nitro" because of their composition. Semi-smokeless propellants used in small arms are either single-base (nitrocellulose) or double-base (nitrocellulose, with nitroglycerine adsorbed into the colloidal paste). Cordite Mark I was 37% nitrocellulose, 58% nitroglycerine, and 5% mineral jelly - a double-base semi-smokeless Nitro propellant.

Under the 1887, 1896, 1904 and 1925 proof rules, Nitro proof rifles were marked with service load they were proved for, including the name and amount of the semi-smokeless propellant proved for and the heaviest bullet used in the normal load. The 1954 rules of proof eliminated this mark and simply marks the proof pressure instead. The above rifle has simply been re-proved. So, "Cordite 80 - 570 MAX" is the service load mark from the 1904 rule marks on the rifle. The "3250 BAR" mark is the new pressure mark from the recent re-proof. Both marks represent the same load. There is no difference.
---------------------------------------------------------------------------------------------------------