The Mossberg 810 was a long action version of the short action model 800. It was available in 270win, 30-06, 7mm rem mag, and 338win mag. It was manufactured between 1970, and 1980.
As far as function goes, I have only ever held one once, and I never shot it. If I recall, it felt like a reasonanbly built inexpensive sporter for it's time, much like the current Mossberg rifles.
Mike