I'm aware of that.Actually, Gaara outright stated he hardened the sand with theYou must be registered for see links. It isn't too far fetched to assume Gaara's normal sand can be pushed by Kimimaro's bones. The finger bullets happened earlier on in the fight, and I'd think Gaara didn't start gathering too many minerals at that point yet.
Kimi also hardened his bones to the max too, it wasn't just Gaara who maxed out his powers.
Gaara's regular sand > Kimi's weaker bones.
Kimi's normal bones CM2 > Gaara's regular sand.
Gaara's hardened sand > Kimi's CM2 hardest bone.