I could be wrong, but I'm pretty sure that the magazines for either cartridge are interchangeable, I've also heard that it's a common occurrence for them to get swapped during a rifles lifetime. I would try to load the mag and cycle it manually and if all seems well then I'd shoot it.
thanks guys. One other thing would any of you have any web sites to get some information on it. Maybe a manual or somethhing I would like to be able to clean it better then just the barrel. I googled the sportsman 74 and I cant find much of anything on it almost like they were never made lol. Any help would be great.