I recently came across a used Bushmaster CAR - post ban (1/9 twist barrel, A2 stock) for sale at local shop for $700.  While I couldn't really figure out how much use it had, it would appear that someone used it pretty regularly, as the top of the stock was worn to a different sheen than the rest of the stock.  Is this a good deal?  I was thinking of maybe buying it and trade the upper for a 6.8 flat top ...

Thoughts?

You would do better to simply buy a lower, and then buy the upper that you want.

I think that price is a bit high. I've seen used Bushmasters for anywhere from $500 to $650. $700 sounds too high. And yes, I did buy the one I saw for $500.