@Sash got it right. At least some, maybe all, British produced Mk VII standard ball ammo used Cordite until the end of its production life. There were 'z' (non-Cordite) 303s - some in other marks that needed a denser chopped nitrocellulose; or a cooler burning powder for high round-count use in automatic weapons; or were standard Mk VII ballistics but loaded in North America with their powders including US Lend-Lease supplies. One of these interesting historical footnotes is that the very popular Hodgdon BL-C(2) powder started out as a Mk VIIz propellant. The Olin Corporation's Winchester-Western ammunition division was completing a huge Mk VIIz Lend-Lease order at the end of WW2 which HMG promptly cancelled. They were demilled and B.E. Hodgdon bought the powder calling it 'Ball Lot C'. As WW had a trademark hold on the word 'ball' for propellants, Hodgdon renamed it BL-C and it was a huge hit with his customers. When the surplus 303 powder was used, Olin produced a replacement in the form of the powder that derived from that old 303 propellant and adopted as part of its contracted T65 development work for the US Army which in turn became the 7.62mm Nato cartridge. Initially at any rate (things may have changed over 70 years), the new grade, renamed H. BL-C(2), was as per Olin's 7.62 M180 ball cartridge powder, but with the flash suppressant coating omitted.
The Hodgdon story is an interesting one. Here is one version of it: "Praise the Lord, and reload the ammunition" to paraphrase.
An Official Journal Of The NRA | Hodgdon: The Inside Story
Lots of bad things happened around that era, the Americans were very jealous of our superior technology, and forced cancellations of all sorts of things things like TSR2, Blue Streak, Black Night, even were anti Concorde. later.The 280 British was chopped nitrocellulose from day one, hence its designation as Rifle Cartridge 7mm No.1z during its brief period of official adoption at the tail-end period of the post-war Labour Attlee government (in the face of fierce opposition from the USA and threatening to derail the creation of NATO as a military entity as the US were insisting on a 30-cal design, in effect their T65E3).
From the New York Times:
Dec. 28, 2006
LONDON — Britain will transfer £43 million to the U.S. Treasury on Friday, the final payment on a debt used to finance the World War II defeat of Adolf Hitler and Nazi Germany.
The U.S. extended $4.34 billion in credit in 1945, allowing Britain to stave off bankruptcy after devoting almost all its resources to the war for half a decade. Since 1950 Britain has made payments on the debt, the final payment of which is worth $84 million, at the end of every year except six.
At the time it was granted, the loan strained trans-Atlantic relations. British politicians expected a gift in recognition of the country's contribution to the war effort, especially for the lives lost before the United States entered the fight in 1942.
"The U.S. didn't seem to realize that Britain was bankrupt," said Alan Sked, a historian at the London School of Economics. The loan was "denounced in the House of Lords, but in the end the country had no choice."
The loan, the equivalent of £119 billion in today's money, was double the size of the British economy at the time. Today it's a tiny fraction of Britain's £550 billion debt burden, about 36.4 percent of the economy.
Ed Balls, the British Treasury minister, hailed the loan as a mark of friendship between the two countries, which currently are allied in fighting in Iraq and Afghanistan. Those conflicts have cost Britain £8 billion since 2001.
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"It was vital support which helped Britain defeat Nazi Germany and secure peace and prosperity in the postwar period," Balls said in a statement. "We honor our commitments to them now as they honored their commitments to us all those years ago."
The need to borrow followed a decision in 1945 by the administration of President Harry Truman to end the lend-lease program used to supply Britain since 1941.
By that time, Britain owed £4.2 billion to foreign creditors, while its income from overseas investments and exports had been halved since before the war.
John Maynard Keynes, the economist and lawmaker who was then the top adviser to the British Treasury, likened his country's financial situation to the military rout at Dunkirk. Prime Minister Clement Attlee dispatched Keynes to Washington to seek support.
Instead of a subsidy, Keynes came back with the loan, fixed at 2 percent interest to be reimbursed in annual payments that were structured like a mortgage. The payments were mostly interest in the early years and shifted toward capital later on.
In addition to the U.S. funds, Canada granted a loan of 1.25 billion dollars, or $1.08 billion at current exchange rates. Britain will also clear that debt with a final repayment Friday.
Germany, the former enemy of Britain, the United States and Canada, takes over the leadership of both the European Union and the Group of 8 industrialized countries on New Year's Day.