As I recall, the M60 shared a great deal of its design with the German MG42 which had the nick name of "Hitler's buzzsaw" due to its rapid rate of fire. The MG 42 had a rollar lock operating mechanism instead of gas operated. IMHO, the US should have directly copied the MG 42 and chambered it for 7,62 withiout other modification. All reports and accounts from WW II were that the MG 42 was as supreme weapon. It was made with simpicity and cost effectiveness in mind - mostly stamping instead of machining - a half of million were produced and used in combat. All the bugs were worked out, and it weighed a couple of pounds less than the M60. Why mess with perfection?

"The Democrat Party looks like Titanic survivors. Partying and celebrating one moment, and huddled in lifeboats freezing the next". Hatari 2017

"Hokey religions and ancient weapons are no match for a good blaster at your side, kid." Han Solo