Picture a rifle as easy to clean as an AK, with an equal ability to keep running when filthy dirty. Then add ergonomics as good as an AR, and chamber it in .308/7.62x51. And the rifle could have been even better - IIRC, it was originally designed to chamber a British 7mm intermediate cartridge (somewhat similar to the 6.5mm Grendel or 6.8mm SPC), which would have made it a lot easier to control in full auto. But the U.S. military insisted on a NATO cartridge with .30-06 ballistics, so we got the 7.62x51 NATO instead (not that it matters to civilian shooters ;^)...
I believe the first prototype of the FAL was built in 8mm Kurz. It’s a pity the intermediate cartridge wasn’t accepted at that point.
And then there's the British EM-2 type rifle, to be known as the Rifle No.9 Mk1, for which that Brit 7mm [.280] round was developed. Those names were better known than the *Janson rifle*, [Stephan Kenneth Janson was the Anglicized version of the Polish firearm designer Captain Kazimierz Januszewski].
Add in the ,280 Tade3n Gun which was planned to replace the Bren and Vickers guns then in service, and the Brits would have had about a 50-year jump on everyone else.
