This discussion started in the comments section of the previous post, but I’ll break it out here. I’ve mentioned this stuff before in various places (as have others) but here it is in one place.
The recent Sources Sought Notices for infantry weapons require a light machine gun (LMG) variant to replace the M249 squad automatic weapon (SAW).
I think there’s a place for both the 5.56 SAW and the 7.62 LMG (though, as always, maybe a 6.8 compromise would work). The lesser stopping power of the 5.56 isn’t such a liability in the SAW role, as it’s mostly setting base of fire and holding bad guys in place, so the “more ammo” argument carries a lot more weight (so to speak) with a SAW than it does with an assault rifle.
But there also needs to be a heavier LMG to do the dirty work.
Even if the new assault rifle goes to 6.8 (which it almost certainly won’t) I think there’s a strong argument to keep the SAW a 5.56. However, I don’t think any 5.56 LMG will replace the M60/M240 role. At least not effectively.
I know that the military would like to have a family of mostly-compatible weapons for the infantry, but compromises mean giving up things. I don’t think giving up too much is too good for the troops on the ground.
We might be best off with a a 6.8mm modular assault rifle with short, medium, and long barrels, a separate 5.56mm SAW, and a separate 7.62mm LMG. If the assault rifle is going to be 5.56mm (as seems likely) then the SAW could be part of that family as long as it has quick-change barrels and heavier construction.
Trying to shoehorn every role into one weapons systems might sound good in theory, but it runs the real risk of giving no one what they need to do their job.