As Fai Mao mentioned in Post 33, the caliber change may be due to the need to penetrate body armor.
From 2018:
https://uklandpower.com/2018/10/31/the-us-army-special-operations-command-usasoc-6-5-mm-precision-intermediate-calibre/
"The 6.8 mm ammunition around which future weapons are to be designed are likely to generate much higher chamber pressures “to ensure that the rounds can still blast through enhanced enemy body armor at up to 600 metres.” Such performance is expected to be achieved by using pressures similar to those of a tank gun, i.e. up to 550 MPa (80,000 psi), instead of usual 5.56 mm pressures of 380 MPa (55,000 psi) for the M855 and 420 MPa (60,000 psi) for the M855A1."
The quote in the article says 6.8mm but the link and the rest of the article cites 6.5mm.
I can see that as a definite plus. But $20 million over 10 years is chicken feed for an arms procurement. This is a long-term test using specialist units as the beta testers.
CC
Needs to penetrate body armor at up to 650 yards? And that is because....?
Just asking. Seems like overkill of specifications.