928m4, thanks for the tip on the BT CH. I posted a thread a while ago asking for feedback and linking to some of the known CH's, but never got a lot of info.
https://www.m4carbine.net/showthread.php?t=55519
Honestly, one thing that would concern me with the one you got from BT is, whether this is a CH from a reputable company that has been proven under hard use. I've not heard of "KZ" before.
Another option for Ambi CH's that I'm keeping my eye on, is Troy's new Ambi CH that is coming out soon, along with their ambi safety selector, mag release, and bolt release.

