Old soldiers don't die. They just get senile. The same kind of sentiments were expressed about their faithful M1903 Springfield when the M1 Garand was introduced.
I'm not advocating hanging on to an old system for the sake of nostalgia. My point was that a titanium 50 caliber is going to cost many times what a steel one costs. With limited dollars to spend, that means that fewer units will have heavy machine guns.
Or just become better engineers: reducing the weight of the M2 won't reduce the recoil of the fired bullet one bit and what was a stable, accurate machine gun will bounce all over the place! The Army engineers are wonderful folks but most of them have zero military/operational experience.
Lightening the weapon will reduce the weapon's stability and will require extensive redesign of the weapon's internals (it is a recoil-operated weapon, nicht war?
There is also the problem of heat dissipation since the M2's barrel acts as a huge heat sink during firing and lightening the barrel will also reduce the numbers of rounds fired before the barrel has to be changed - right now, with the steel barrel and stellite lining, it's about 400 rounds fired in short bursts. After that, the barrel blows up!
Anybody remember the goofy M60E3? The army put a skinny barrel on that puppy for "walking fire" (a useless concept, if there ever was one) and within a few bursts, the barrel melted and the rounds exited the side of the barrel!
The M2, as designed by John Moses, is a superb, proven, dependable and incredibly versatile weapon. I have fired well over 200,000 rounds through them over my 27 years on active duty and I am also an experience mechanical engineer - don't fix what ain't broke!