Colt does not use 4050 aluminum anywhere. They use 7075 T6 Type-III hard coated aluminum for the upper and lower receiver, and are one of the only companies to use a proper extruded 7075 receiver extension.You may be getting confused on the barrel which is 4150 CMV(probably the best barrel material for a combat rifle).To the OPOptic: Trijicon SRS02 is by far my favorite.Foregrip: so many out there its all up to you.Bipod: I usually do not use one as I just mono it from the magazine.Laser/light: ignore the laser, they generally have a visible range of 20yards so unless running lots of NV they are pointless. For the light the XM300 is a great option, its light small and easy to use when your thumb.Magazine: i use Lancer AWMS, they feature a hardened steel wraparound feedlips that are near impossible to break, feature a constant internal curve designed for the taper of the 5.56, and are very durable.I will say for a battle rifle it's very good but cheap materials. i.e., carbon steel barrel strong but prone to rust. Carbon steel barrel extension, again prone to rust. I have learned there are better materials than "Mil spec" which really means bare bones. In other words there are a lot of stuff better made than Mil spec and from talking to many GI"s. they tell me they buy their own bullet proof vests because gov issue are junk. Looking back I would have bought the Wilson Combat. ie., the 6940 uses cheaper 4050 aluminum where wilson uses premium 7075. also wilson uses stainless steel for barrel. But I still like my Colt and will hang onto them.