My neighbor has a well worn 77F 20 that I was checking out the other weekend that has a really sticky pump on the return forward to lock up the bolt.  So I told him I'd rip it down and give it a good once over without really knowing a dn thing about the model.

So what am I in for disassembly wise?  I'm going to hit YouTube and Nirmrich for a schematic of course, but any tricks or follow I need to adopt or avoid?  I'm hoping the action is just gummed up from 50 years of existence, but we shall see.

The Stevens 77 is a nice shotgun IMO. I picked one up for a song last year because it had a similar issue. Ended up just needing a good cleaning. There are a few videos on YouTube which were helpful to me. It can be a little intimidating the first time you strip it down completely, but they're pretty simple to work with.

I see these older American made shotguns as diamonds in the rough. They're made with blued steel and walnut or hardwood stocks and can usually be bought for a good price.