I have a standard spring and H buffer in my work gun which is the same upper with a Larue 10.0 rail. It’s the old BCM without the logo on the upper and one of their older FA BCGs. Many thousands of rounds with no issues.
Sprinco RED carbine spring, and H3 buffer are what I run in my KAC.
It runs real nice. Suppressed, and unsuppressed.
I don’t shoot anything under 62 gr. though.