[Suhiir]

To the best of my knowledge the US Army regularly used M60's as LMG until the advent of the M249.

For my part I'd agree, ignore the M28.

They're no more useless vs armor then anyone else, and actually much less as many WinSPMBT US/USMC squad variants have a bazooka.

The USMC continued to (and as far as I know still continues) use M14s for some roles till at least the mid 1980's (the last infantry battalion finally got M16s in 1971). In fact in 2001 the M14 was officially re-introduced as the "squad marksman" rifle (since replaced by the SAM-R).

From talking to some of the "old farts" when I first went in (some dated back to WW II) the problem with the M14 AR (M14E3 I believe) vs M1918A1 BAR was 3-fold:
1) The M14 had a lighter barrel this heated up much faster
2) The M14 bipod was an add-on and not very sturdy
3) The M14 wasn't designed as a full-auto weapon thus wasn't very "sturdy"
All-in-all the M14 was a poor substitute for the BAR. But in the interests of standardization it was pressed into the role (as was the M16).