Hi leathersmith, welcome to the forum! I think your idea of sticking to one brand of ammo is wise, just to eliminate some of the variables. If it works for a couple hundred rounds with the Magtech, then try some other brands. Sometimes it takes rounds down the barrel to break in certain weapons, I personally think they should be "broken in" before they leave the factory. Anyway, let us know what happens 
Regards,
Mike
Regards,
Mike