I have used Promag AR 9mm mags. They worked for me, held bolt open. Everything else they make seems to be sub par at best.
C products mags didn't hold bolt open with out modification.
Metalform - Home Metalform used to sell to public. Doesn't look that way anymore. They seem to have the best...
OOPs
Even if the bullet did not hit the roof, notice the powder burns on the paint.
I have taken a few shots across hoods and truck beds. Never shot into them though.