Olympic used cast lowers as late as 2004. I have seen gaps between the upper and lower, uppers and lowers that would not interchange from one rifle to another, fire control holes drilled crooked and out of dimension, chambers that looked like Century Arms did them and fire control components that were not hardened correctly. It sure is funny how when I am cutting down a front sight base fom a Stag, Bushy, Rock River, DPMS and similar I get a nice shower of white sparks that flare nicely and then the few Olympics that I have done shed dull orange streamers. That is a sign of poor quality steel.
You get what you pay for.