Unfortunately it's impossible to go through an entire modeling session based on text on a forum. The real and not the shinning answer you would like to hear is, you have to watch a lot of tutorials and practice a lot and make lots of mistakes and your brain will slowly start to get it. We can help along the way and get you out of a bind, but you have to put in most of the work. Modeling is one of those things that come from the intuition more than anything, so you have to develop that. Luckily is a fun road.
Also, sometimes it can be helpful to model different parts "separately" (still in the same mesh) and then figure out later how to connect them.
This is low poly but a decent place to start. https://youtu.be/K6_hbdaqdO0?si=DRXK1bNTuHHhAm6j
...and the (older) Mesh Modeling Bootcamp has a revolver modeling chapter: https://cgcookie.com/lessons/revolver-pt-1-block-out
Might be helpful as well.
