Most M60 machine gun ammunition was 146-gr M80 ball, 146-gr M62 tracer, or 150.5-gr M61 AP. There was originally the M60 HPT 172-gr ammunition for the machine gun.
The 172-gr M1 ball was developed for the Browning 1919 machinegun in .30-06. When the M60 was originally developed, it was in .30-06. I will post of a photo of one, the TE-162, linked up with this 172-gr ammunition.
The 172-gr carried over to the M60 in 7.62x51mm as the 171.5-gr M60 HPT (HP = high pressure, not "hollow point"), charged with IMR-4475 powder at 67,500 PSI proof pressure. Since the original .30-06 M1 172-gr ball was minimum 2,640 FPS from a bolt action rifle, that was the spec for the combat issue M60 equivalent. Since that is too much pressure for the Garand, it was also too much pressure for the M-14.
The 172-gr M118 Special Ball was the boxed match ammunition loaded with WC-846 or IMR-4895 at 50,000 PSI and 2,640 FPS.
