FC2 here... My opinion is that FC is the best rate in the Navy. Then again, most people will say that their rate is the best in the Navy. As for what your responsibilities are, it will all depend on what type of FC you end up being. Once you get to Great Lakes and pass your schools, you will choose what is called a C school. C schools are where you learn how the specific equipment that you will be working on works. All of the schools you go through up in Great Lakes will teach you the basics of electronics and such. Depending on what C school you go through, that will determine what your job will be. For me, I am an Aegis tech. I work on the computers that run the Aegis system. There are ALOT of different FC's. Some work on radars, some work on computers, some work on display consoles, some work on guns, some work on missiles. If it has to do with firepower, there is an FC involved.
As for how hard it is to make rank... It all depends on what the Navy needs at the time. 5 years ago or so, it was practically impossible to make rank. The test cycle I finally made E5 off of, they promoted 27 out of 750 or so. It was the 3rd lowest advancement % in the entire Navy. It was even worse to E6, with only 7 out of 329 advancing. However, at the present time, it is unbelievably good for FC's. The last test cycle, they advanced 72% to E5. The %'s will change from cycle to cycle, depending on what the Navy determines they need at the time. So, there is no hard set answer to how easy or hard it is. Just a matter of chance of being eligible at the time they are promoting alot, ya know?
Well, I think this is long enough of a book. Good on you on choosing a good rate, and if you have any other questions, shoot me a line. Glad to help...
FC2