I also run the Reminton green box and UMC in my Uzi and Colt 9mm SMG, and have for years. I would like to mention that not only are my Mac's factory correct, but every other subgun I own is as well. If you are not running a factory Mac, and you are experiencing reliability issues, it's because you are operating a Mac that has been monkeyed outside the original specifications and is at best, a boarderline contraption. As far as what brand of ammo will make it easier to pull doubles, I can pull consistant doubles in any of my Mac's, with any brand of ammo I choose, standing on my head, going down a flight of stairs in a wheel chair all day long. My advice to you is be carefull of the information you get on Mac's in general, because most, if not all of it, is based on nothing more than myth and non factual Bu#!Shit.