E4 upgrade kits for registered M60s are available, even if newly-manufactured guns are not. It knocks a couple of pounds off the Vietnam-configuration *pig* and improves reliability considerably. And at least a couple of registered M60E3 versions have changed hands recently.
I was sort of thinking MG82/MG25 Amelis and HK21s and 23s, however. And then there are some Stoner MK23 MGs in private hands....Pricey, but available here and there. But not what I'd get if I were so inclined.
You can have a macine gun post 1984, if you have a class 3 FFL.