Is it OK to say: "Load up on guns" with these words starts "Smells like Teen Spirit" by Nirvana?
Yes, 2008. It's correct -- colloquial, but correct.
Get yourself a good (big) dictionary, and get a competent tutor to teach you how to use it. An enormous number of phrasal verbs are listed in dictionaries. You just need to learn how to locate them. If you had looked in the Merriam Webster's (free) online dictionary, you would have found 'load up on,' and a quotation by H. L. Mencken (a great essayist, by the way) in which it is used.
Mark in Rocky Gully.