I was in wal mart today and heard of some people seeing ARs in theirs so I decided to look. They actually had two and I was very surprised. They had a dpms one that was $5xx and a Sig Sauer one for $917. The sig had a bunch of magpul stuff including rear folding sight, front sight, extendable stock, grip, and foregrip. They were both listed as .223 caliber, and the guy told me that it would shoot 5.56, but i thought I had read somewhere that .223 wouldnt fire 556 but that 556 would fire 223. Did i read wrong? What are your general opinions on this gun and price.