JP does not use a weight in their AR9 bolt.
Nor do they use a heavy buffer.
I removed the weight from my CMMG bolt and replaced the silly heavy buffer with a JP SCS.
It's a whole new carbine. Splits went down easily 25%.
The downward "dot dip" that all the reciprocating forward weight caused was gone.
Thousands of rounds later, not a single problem. Full disclosure, I did break a bolt catch same day I installed the SCS.
I replaced it with a Seekins and it's been fine, I think it was just a cheap part.
I had a Slash 9Q prior to the SCS.
I'll never go back to that clunky heavy buffer system. It sucked.