I just bought a set of the magpul BUIS, and for the price I'm happy. As long as they stay down when I don't need them, and are available as a BACKUP for my red dot going down, why pay more?
I bought my front and rear for $80. TOTAL.BTW, I thought you needed a different lower to use 7.62x39 than the standard .223? I thought that's why we have 5.5 and 6.8 fighting it out.
I found a used eotech 512 for $200 on AR-15. com and love it. Its got a one minute dot and is bright enough I can point it at a white roof in the Fl. summer sun and it doesn't wash. Plus it uses AAs which I consider a bonus.FQ13