I just got a H3 buffer for a 9mm build. The thing rattles. Is this normal?
I am thinking of jamming lead in there to get rid of the rattle. Either that or silicon .

H3 has weights. Yes it will rattle.
If you don't like it, I will trade you a 9mm buffer for it.
No rattle.
Dave N

Thanks for the offer. I will just go with the H3 and if I can here the rattle shooting with a can I may take you up on it.
May be a while since I can not find a 9mm bolt.

In my own industries' jargon - "that's not a bug, it's a feature."

The rattle is there on purpose - the weights freely slide forwards and backwards a small amount.  During cycling, as the bolt finishes moving forward  and strikes the barrel, it will have a tendency to want to bounce backwards off the barrel momentarily (physics being what it is and all).  During full auto fire (or rapid semi-auto fire), this bouncing can cause stoppages if it overcomes the force of the recoil spring.  The sliding weights help to counteract this - about the time the bolt hits the barrel and begins to rebound, the sliding weights will reach the forward-most point in their travel inside the buffer, slamming into the front portion of the buffer.  That in turn causes the buffer to transfer a little extra "oomph" forward into the bolt, usually nullifying the bounce-back.

Hope that helps,

-bob