I bought this from Airsoft GI in 2011 for $450. I will tell you that after owning it for over a year, I am not very pleased with it. This gun had so much potential to be a great reliable gun, but I've had nothing but trouble with it since my first game.
First Impression:The gun looks amazing! It has licensing info right from FN Herstal. The lower receiver is plastic, as well as the adjustable stock, but that is it. My original gripe with this thing is the battery compartment. Fitting a mini NiMH is a pain, especially with the automotive fuse in stock. The thin wiring shreds easy, and the pin is hard to remove. I bought this with a bi-pod and scope (sold separate), and the thing fired like a dream. I was pulling it with an 8.4v originally. Now I realize that was wrong, but it got it by. I was getting a 6" grouping on a target 50yds away with about 5 shots using 0.25g bbs. I do not know the FPS as of this time. Gun is quite heavy, being made of almost all aluminum.
First Game: The gear box jams after about 5 minutes of game play. I am assuming the 8.4 has something to do with it, so I get it unjammed, and it works fine for the rest of the day
Second Game: a few months later, I use it again, this time with a 9.6 nun-chuck which is easier to fit in the stock. This pulls the spring just fine, but after about 4 rounds of kicking serious ass from a sniper tower, the FPS is noticeably getting lower and lower. Finally, the gun jams again. This time, the gears grind when I try to get it going again with a 12v jolt. I set it aside, and we opened the gearbox a few days ago to find...
The verdict: The piston was stripped, and even the reinforced gear was cracked (pic here: http://i48.tinypic.com/2ivlc29.jpg ). The "automatic shimming" did a horrible job at keeping the gears centered, and when they were pulling on one side of the piston, it got wrecked. My friend, who has over 50 guns worth of repairing experience, re-shimmed and helped me install a new piston (CA Reinforced, polycarb, metal tooth) and we put it back together. The box sounded great, but when fired, the 0.20g bbs just rolled out of the barrel, dropping to the ground at about 20 feet. My Xcortech was not chronying the gun at 145 FPS. After cleaning the barrel and hop-up, the gun still shot slow. We checked the compression before putting the gun together, and it was better than when we took it apart. I am opening up the gun again in a few weeks when I get parts. I am assuming a nozzle or tappet plate issue.
If I was you, I would not put $500 on this gun. It is not worth that much. Maybe $350 would be a better price. This is far to unreliable a weapon to use, and after scouring the internet, you will find the same complaints. Not only that, but being a 7.62x51 receiver, the hop-up and nozzle are VFC only compatible, which makes repairs expensive. The gun looks and feels amazing, but with lackluster performance, the gun falls short of its price-tag.
Fires hard (out of box)
Great RIS platform for mounting goodies
Locking slide, making hop-up adjustment a breeze
Un-reliable, poor internals (auto shims, piston)
Battery compartment woes (thin wiring and tight fit)
Ambidextrous fire selector is loose on right side (design flaw)
Hop-up and nozzle incompatibility (upgrade/repair difficult)
Current unknown flaw with FPS (after about 8 hours of total use on the gun)
poor wiring (inside handle with motor as well as battery, which was already mentioned)
Rating: [2 of 5 Stars!]