If it's an aluminum receiver with the built in rail, and came from Century, make sure its got a serial #007000 or earlier. They were (are?) built on used FMP parts kits with the Federal reciever. It seems the early one were put together well, and the later ones were hammered together by chimps trained by gorrillas (internet speculation).
I got two in 99, paid $600 or so each, and they have run pretty much flawlessly with a couple of thousand rounds through them.
I've had a few FTF's with one lately. I may be getting light primer strikes with one now, or it may be the crappy Malaysian ammo I've been shooting, I'm not sure.
I had a weak extractor spring in the other one. Fixed that and it's run like a champ ever since.
If the price is around $300, and the serial is below the threshold, I'd buy another in a heartbeat. Even with simians putting the parts together, it's hard to make the things malfunction. It's an HK design after all!