Many of my guns have been "different" because like most of you, I'm nothing more than a gun but trying to learn something new. A lot of these guns have something unusual about them and there's no reason not to refer to the owner's manual if you want to take it apart and put it back together, just like you used to try to do with clocks. It is surprising how different S&W autos are from Colts, for instance. But I'm still afraid to attempt to dissemble a Mauser bolt.
Really good owner's manuals come in four languages and have photos of models not sold in this country, always pleasing to an afficianado, but if you're lucky, one of the languages is English. One of my manuals is in German but the photos are sufficient, almost.
My late father-in-law was an engineer. He loved manuals and would annote all his manuals with additional instructions together with his opinions, usually negative, but I never do anything like that.
On the subject of manuals and such, anyone remember the old, what was it, PM Monthly or something like that that the army used to have back in the late 60s?