I've heard the same hit or miss feedback as well, though I don't have a Century. I don't think 1MOA at 150 is not out of line for an HK91 clone. But like Jose said, it's a battle rifle, not a tack driver.
On an HK91, the headspace is the important thing to check. The ad says it is "perfect", but I would ask for the actual measurement (spec is .004-.020 in.) and also ask if that is with standard rollers or if it has oversize rollers to get it in spec.
If you buy this rifle, feel free to PM me and I can set up some downloads for HK manuals for you.