i know i am one of the worst to buy cheap AR stuff.
lately i have been on a cheap-o binge on buying AR parts.
so far i have done very well. i all ways double check everything and assemble everything myself. if i was forced to buy from some shady company i would probably tear down their upper and check everything--just to be sure.
there are pitfalls to going to cheap. when you start buying AR-15 parts from the bottom feeders on the market you are rolling the dice.
the most critical things are the barrel and the bolt carrier group. if these two parts arn't correct you can end up like the photos.
canted front sight/gas blocks are pretty common and usually can be fixed fairly easy.
improper chambering, gas ports drilled through into both sides of the barrel are pretty common ails for the bottom feeder AR-15 kits and generally arn't fixable without a barrel swap.
another thing that worries me about the very low end sellers in their bolt carriers. improper heat treating, out of size --lots of things that can go 'boom" in the night--LOL
if you are lucky you can get away with a bottom feeder build. if your not so lucky you likely spend more getting the thing up and running than it is worth.
my advice is spend that extra $50-$80 on a known quality kit from well established vendor.
saving that $50 is it really worth the trip to the ER?--LOL