Ur a heck of a photographer pepper! I agree with pauli that an mpi'd bolt is a good spare part. First thing I always change is the pistol grip(I like ergo grips).
There are a cubic shit ton of AR accesories to hang on an AR, but most guys don't use/need half the crap they put on. All it ends up doing is costing money and adding weight. The easiest way to figure out what u need is to ask urself what u expect the weapon to be used for. Hunting, home defense, SHTF....Ammo, mags, and cleaning supplies are always good to have more of
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Training is a good idea as well. "Be afraid of the man with one gun, for he probably knows how to use it"