how do i fix a wobblie bottom on my ris the bottom rail moves from side to side.. any ideas?

If you try to shim it and it still does not work you could get a Knight's Armament UK-SAS lower rail w/clamp.

This lower rail is an upgrade to the standard M4 RAS or RIS lower rail.

It clamps on to the barrel nut instead of just being held by the delta ring.

where can i find this piece you talk about?

Quoted: where can i find this piece you talk about?

As we all know how hard it is to find any Knight's parts these days but once in a while they are available.

Here's a link of Operation Parts which also supports this site. It's the fourth product in that webpage, look for "Knight's Armament UK-SAS Lower Rail w/Clamp".

Other KAC dealers are MSTN and Impact Guns which are also industry partners.

You could also try to contact KAC in the Industry section or their website.

KAC website link

Good luck.