Interesting

[Bruce_in_Oz]

I was under the impression that Mk 7 Z started out in the aerial gunnery biz, Cordite has a well-earned reputation of muzzle flash, granulated Nitro-cellulose, less so. A tail-gunner in a 4-gun Lancaster turret would be dazzled by his own muzzle-flash if "standard" Cordite ammo were used. I also suspect that the "Z" used in Mk 8 Z was a bit slower-burning than Cordite; better for use with marginally heavier bullets in longer MG barrels.

In the First Great Unpleasantness, US factories NEVER used "Cordite to fill .303 ammo for Britain,instead, they used the same type of stuff they used in their "sporting' ammo in that cartridge.. The Canadians made BOTH styles of ammo; Mercuric-primed, Cordite-fueled stuff at the "government" facilities and Boxer-primed, NC powder-fueled at "commercial" plants.

US factories also churned out vast amounts of 7.62 x 54R and 8mm "Lebel" in WW1. As long as it was reliable and had similar ballistic behaviour, it was acceptable. The subtleties of variations possibly affecting performance or whatever, were irrelevant.

Some of that WW1-vintage, US made 7.62 x 54R ammo made it to Oz in the late 1970s. Good stuff, especially in Tokarevs. which, in the "good old days' were more common here than Mosin Nagants.