FWIW:
Various references I have read today confirm the use of "W.R.A. 30" and "W.R.A. 31" as a Winchester cartridge head-stamp in 1930 and 1931.

Winchester introduced "Staynless" primers around 1929. They superseded the "NF" (non-fulminate) primer, "which was somewhat copper in color", according to one collecting source. I assume the 'Staynless primer' may have been silver in color (?).

In the 1920s, Winchester began using a Lubaloy (copper) plating on lead bullets, (while Western Cartridge Co. was also using that term on copper jacketed bullets).

I don't know if Winchester had adopted copper jacketed bullets by 1930.

The Western Cartridge Company purchased a bankrupt Winchester R. A. Company on 12-22-1931.

It would be real interesting to see the base of one of Jeremy's bullets to see if it is marked with a "W".