I just bought my first conversion kit from CMMG and it fails to grab the spent casing about every other shot and tries to feed the next round up the tailpipe of the other.  Sometimes if I'm lucky I can get about three shots downrange before having to take the mag out, pick up the scond round(now gouged and of no use) get my knife and get the spent casing out.
Any ideas?

I put about 200 rounds through it and it's marginally better. I may get 8-10 rounds before having to dig out an empty case.
Thanks for the link. I'm going to keep trying and hope it improves, my eight year old is dying to wear it out!
Oh, I did notice the lip of the extractor isn't straight across, it has a high side toward one end.I don't know if it is a bur or what but hopefully it will wear off.