It is hard to find the original sources of these experiments because these experiments were done in 1980s, an age that people did not always upload articles on internet. Fortunately, I got a 1994 report about NON-US ELECTRODYNAMICS LAUNCHERS RESEARCH AND DEVELOPMENT. It describes the development of EMG of Russia, German, UK, Japan and China.
https://digital.library.unt.edu/ark:/67531/metadc686699/m2/1/high_res_d/45558.pdf
This is the description about Chinese 303EMG and other EMG device: "The best performance given for
the square-bore gun was 3.2 km/s with a 30.2-g projectile and, for the round-bore gun, greater than 3 km/s with a 100-g projectile." (Page III-5)
If you see the report that I posted and other reports from IEEE, maybe you will believe the "chinese shit".