The M37 was used on M60 tanks, maybe some tanks still needed 30-06 ammunition.
I don't know about the M60, I'll have to check my references to be certain, but I don't think it was a .30-06 mg.
I DO know for certain about the M60A1 and all later variants' .30 cal guns, and they are NOT .30-06.
The M60 series tanks used the M73, then the M73A1, then the M219 machineguns, in 7.62 NATO. The M73 was a crap design, the 73A1 tried to improve (failed) and the M219 tried to fix the 73A1's problems (failed, again).
Finally the entire series of M73based guns was replaced in the late 70s with the M240, a version of the Belgian MAG58, also in 7.62mm NATO and a much superior gun to its predecessors.
I'm sure there was a reason LC kept making 06 ammo, possibly even one beyond simple govt intertia.
Didn't our services field .30-06 sniper rifles through Viet Nam? Also Nat Guard and Reserve tend to have officially "retired" equipment on active use for some time. And I think the Navy kept a number of Garands for shipboard use for some time, eventually converting many to 7.62mmNATO.
Any reason can be enough to keep an established govt program in operation long after its main reason ends.
The only thing that lasts longer than a temporary govt program is stop-gap spending. The most useless, obsolete wasteful projects seem to have eternal funding, and something that might actually be worthwhile (like the project YOU work at) gets its budget cut every time the wind changes direction outside the Capitol building. Or so it seems (and yes, that is a bitter, cynical personal observation. I'm mostly over it now...
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