Be sure it aint any fat etc. that its totaly clean when u paint it again, and if the old paint is glimmering off you got to take remove all lose paint or it will start to glimmer off with ur new paint...
only worry about stripping if the old coat isn't sticking. otherwise you can get three or four paint jobs before stripping depending on how thick you lay it on.
I've painted a few rifles of mine... and I agree that yes you can just paint over it. Loose paint... scrape it off and be done with it. More layers the better. Ugly it up!!!!!