If you're going to be going through a major city there's a decent chance you'll go through a metal detector / get searched on the greyhound. It's been a while but I've seen it in PDX, Reno, SLC, Dallas, Houston, NYC and I'm sure I'm forgetting a couple. It's pretty much a crap shoot. Sometimes they're scanning / searching everyone, sometimes they just wanna get you outta there. If it's a small knife buried in your pack I really doubt they'd take it even if they found it. A Bowie knife or anything like that they're just gonna confiscate off you. A gun will catch you a charge in the wrong state.