At that price, I'd take it. If you do, think about a red dot type scope for it. A friend of mine has one set up that way and it's a blast to shoot. I've put at least 500 or 600 rounds though it myself, and I've yet to see a malfunction or FTF. As soon as I get the heck outta this state, or we get some of these socialists out of office and repair the damage they've done, I'll be in line to get one myself. Plus, they are still in production, so parts are very easy to find. One thing you may want to check is which version it is. The early pre-bans have no iron sites and are an "optics-only" deal. The very last batch of pre-bans had both the flash suppressor AND the iron sites (with the see-through scope mount). These are the most desirable. The post-ban version has the iron sights and no flash suppressor or muzzle brake. These are easier to find, so they tend to be a little cheaper. Either way, a price of $650 - $700 is good for a new one, with used running from $500 to $650 (post ban) to $750 (pre-ban w/ sights). Sounds like the one you found is a pretty good deal especially since it comes with a scope (assuming it's in good shape). If it's a pre-ban, it's a steal. I'd go for it. If you decide to get it, let us know how it works for you. Good luck.
-John
