The M60 "borrowed" design features from the MG 42 (notably the feed cover mechanism and the extensive use of stampings), the Lewis gun (bolt group), and I believe the BREN gun (barrel latch).
Touted as a wonder weapon, the only thing it did really well was be lighter than previous guns, at 23.5lbs. The feed system (in the cover) was nearly an exact copy of the MG 42's, and worked pretty well, however, the feed tray itself was crap, being too thin (and a stamping), which was prone to crack and the rivets fastening the hanger constantly came loose.
The bolt group wasn't bad, but the designers choose poor angles for the cam surfaces between the bolt and op rod, resulting in the gun actually chewing up the op rod during operation. Can't tell you how many op rods I stoned to keep them running for a while, but it was more than a few.
Also, there was no secondary sear, so that when the trigger was released, the notch on the op rod would slam into the sear (and the op rod would also ride on the top of the sear as it worked, if the trigger wasn't held back enough) resulting in rapid wear of the rod, and the sear, which eventually would lead to a run away gun.
And, instead of working smoothly like the MG 42, the M60 was very jerky when feeding, the vibration was bad enough to overcome the spring detents and allowing the end caps of the gas cylinder to virbate loose. We wound up using lacing wire to keep them on, and that meant that the wire had to be cut, in order to disassemble the gas cylinder to clean it, and new lacing wire installed afterwards.'
Other flaws in the execution of the design were that the carry handle was on the gun (forearm) NOT the barrel, (unlike the Bren) so one needed the asbestos mitten (provided) in order to change a hot barrel without serious burns.
AND, the bipod was mounted on the barrel, not the gun, meaning each barrel assembly was bulkier, heavier, and more expensive than it needed to be, because every spare barrel also had its own bipod attached!
AND...the trigger group was held to the reciever by a single solid pin. The pin was retained by a leaf spring, which could vibrate off, or be brushed off, and was easily installed upside down, which meant it would remove itself due to gravity somtimes. And when it did, the pin was easly pushed, or vibrated out, letting the entire trigger group fall off the gun! If this happened with a belt loaded and the bolt back, the gun runs away and keeps firing until somthing jams the belt or it runs out of ammo!
All in all, the original M60 design was a fabulous gun, if you were a manufacturer interested in selling as many spare parts to Uncle Sam as you could. If you were the troops using it, at best, it was adeqate, and seldom was it at its best.
A fine example of a gun designed by a committee, taking the good features from some other guns, and putting them together in the worst possible way.
And yes, I worked on them....a lot.
I'd have to go look it up, but I don't think its correct to call the MG 42 a redesign of the MG34. The bolt groups are quite different. While there are many visual similarities overall, they are mechanically quite different at the heart of the gun. IIRC, the MG42 uses a variation of the roller lock system (actually a delayed blowback, but without the fluted chamber found in the H&K version), while the MG 34 uses rotating bolt locking lugs (might be wrong, but that what I remember. After I look it up, if I'm wrong, I'll apologize.
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