I've used Federal bulk 550 packs from walmart with no problems.
I've also used some aguila 60 gr SSS (subsonic) rounds, but not enough to recommend them to anyone yet, but what I have shot, I've not had any problems.
I've used CCI---no problems
I've used Winchester bulk packs--a few failures with them, but nothing terrible.
As for the backorder status, good luck with that because there's a lot of folks waiting on them right now. And I'm talking with some major companies like Brownell's and Midwayusa.
For what it's worth, Midwayusa sent out a courtesy email about them back in stock last week, but they sold back out the same evening.
I have a buddy in Arizona that ordered one directly from Ceiner around the middle of December. He still doesn't have it and that's been almost exactly 3 months ago.
Edit to add, 27 round, Full size Black Dog mags ROCK!!!!!!!!