How do I actually report a scam call on FCC.gov

The online form for reporting an actual scam call on the FCC.gov site is not convenient for reporting out-and-out scams.
http://www.fcc.gov/complaints
The choices that seem closest are :
(*) Telemarketing, Prerecorded Messages, Caller ID Spoofing, and Do-Not-Call
(*) Wired Telephone
(*) Wireless telephone

None of the subtopics actually have "scam call" or anything like it. Most seem to be complaints against legitimate entities performing illegal actions.
E.g. :
"Telemarketing, Prerecorded Messages, Caller ID Spoofing, and Do-Not-Call" -> "Unwanted/unsolicited telemarketing calls (including Do-Not-Call) received on your home telephone" -> Form 1088B

This form asks for a lot of information as though the caller was a legitimate entity (business with prior relationship, non-profit, etc.) but does not have a field to actually report the modus operandi of a fraud.

I had a similar problem with the Florida state DNC list--which I'm on.  I filed a complaint about an outfit called "All American Air" who was calling about a "free" inspection of my air conditioning system.   (They were rated "F" by the BBB.)   While I reported the company name, I couldn't provide the called ID name or number because they came up blank, no doubt intentional masking by the caller.  The Florida DNC later sent me a letter stating they were closing the complaint because I couldn't provide a telephone number.   "Duh."

Your at the wrong government organization for making a complaint like that.  The FCC handles communications.  Where you need to go is the Federal Trade Commission (FTC.GOV).

Here is a link to the page and you can then find the category you want to make the complaint under:

https://www.ftccomplaintassistant.gov/#crnt&panel1-1

Furthermore if it is a credit or debt related complaint you can also file a complaint at the Consumer Financial Protection Bureau (consumerfinance.gov here:  http://www.consumerfinance.gov/complaint/

There's a form on: https://www.donotcall.gov/ as well. I doubt that anyone on the other end really looks at it though as the "do not call" list itself is pretty much a joke. May keep honest businesses from calling you but it does nothing for the majority of telemarketer spam calls for Health Insurance, Student Loans, donations to out-of-state Police departments and etc.
Anyway, the link I just provided was working until our government went into a hissy-fit and shut itself down. Now it's down and probably won't come back up until the Trump wall is built.

You're right - it doesn't keep scammers from calling you. That doesn't mean it's a joke, though. It's simply ignored by criminals, just like they ignore all other laws.
By the way, why did you feel the need to revive a thread that's been dormant for almost 5 years?