yes, it is a real shame that the .280/30 aka 7X43mm, and in production form, the 7mm Ball Mk1z was abandoned under US Army pressure that insisted the new NATO cartridge had to be .30-cal and give comparable ballistics to the .30-06 M2.
The 7X43mm gave a long high-BC 140gn FMJBT 2,450 fps with the propellants available in the late 1940s. Look at the cartridge and it's near identical to the 7mm BR except it has a bit more case-body taper and a more shallow-angle shoulder to function in magazine weapons. The British EM-2 experimental rifle had a very low full-auto cyclic rate of 120 rpm to keep it controllable, and with the 7mm's light recoil, there is a photograph of the Project Engineer demonstrating it to VIPs by firing it single-handed like a pistol, but on full-auto. Despite that it had an effective range (in machine-guns) of 2,000yd and gave better ballistics than the old .303 British at all ranges. It didn't match the .30-06 M2 ballistically to 1,000yd, but bettered it beyond that range! At 2,000yd it had 100 ft/lbs remaining energy -military cartridge designers assume that 60 ft/lbs is sufficent to inflict serious or fatal injury on a human being (but that was in pre body armour times).
What a target cartridge that would have given us today with modern powders for Target and Fullbore Rifle, Palma Rifle etc! There was an attempt around 15-20 years ago by a couple of British entrepreneurs to revive the design and bring it into production as a light to medium deer cartridge, but nothing came of it - not surprising when you've got .243 Win, 7mm-08 etc already there. What's interesting though is how close 6.8mm Rem SPC is ballistically to the old Brit 7mm, except that the 7mm has a larger diameter and heavier bullet that will have greater lethality.
Something that not many people know (to paraphrase Micheal Caine the actor) is that Great Britain was so brassed off by the US attitude that she went it alone and unilaterally adopted the cartridge, the British Army Council and Defence Ministry adopting the EM-2 as the “Rifle, Automatic, Calibre .280, No.9 Mk1” in April 1951 with the personal support of Labour Prime Minister Clement Attlee. A .280/30 belt-fed GPMG, the ‘Taden gun’ (based on the British WW2 BREN Gun) was also close to adoption. The Americans were appalled and how NATO’s smallarms development would have turned out had this stuck is anyone’s guess!
However, Labour lost the 1952 general election and the new Conservative Prime Minister Winston Churchill (yes, the same Churchill who led Britain in WW2) had a one to one meeting with President Harry S. Truman and backed down on the NATO rifle and cartridge issue to protect the ‘special relationship’. The EM-2 couldn’t handle the T65-E3 (7.62X51mm) cartridge that emerged that year, the various design and production teams were disbanded, the EM-2 project engineer left the UK eventually becoming Winchester’s R&D Director. It was the beginning of the end of Britain’s role as a leading military arms designing and manufacturing country, subsequently adopting the FN FAL as the L1A1 rifle and FN MAG machinegun as the L7A1, both in 7.62mm calibre.
There are question marks over how the EM-2 would have worked out in service as it was a very complicated rifle, but FN had already developed the FAL rifle, the oustanding 1st generation assault rifle, in 7X43mm and it was so fielded in the 1950 NATO smallarms trials and beat all comers. After the British climbdown, FN redesigned it for the 7.62X51mm which added 2lb to the weight and whose recoil and barrel heat generation made full-auto fire impractical -still a fine military rifle, but not as good as it should have been!
