Cheap and reliable?? Do you mean less expensive and reliable?
M&P is probably too expensive..
Stay AWAY from Colt..
Bushmaster is iffy on price..
Olympic Arms.. you be the judge ..
I would say DPMS Sportical (No fwd assit) But do you really need that? I've shot over 100K rds in my military career thus far easily and have not utilized but only 1 friggin time and that was a required drill. But im a NAZI at keeping my weapon clean and wet.