7.62x54 Barrel proof

I’ve seen these listed a couple of times on auction as an “autofrettage” made for or by Westinghouse for testing the Russian M91. Does anyone have any info on these? Is the Westinghouse story true or conjecture? It seems like there would be easier ways of obtaining brass than making it from a 303. The headstamp is “U 15 Vll”.


It would be interesting to see this cartridge next to a regular 7.62x54R.