This is 49 CFR 1540.111.

This is the pertinent part of that CFR. I bolded the exact line that's important:
When it comes to TSA-Approved locks, the passenger is not the only one who "retains a key" to open it, as outlined in 49 CFR 1540.111. Obviously. That's the whole point of the TSA-Approved lock in the first place. The end result, however, is that TSA-Approved locks will not be acceptable for securing the hard-sided locked cases containing unloaded firearms in checked baggage.

EDIT: After thinking about it some more, I don't think it would apply since it wasn't a TSA thing in the first place. Henceforth, I have removed it.

Irony, meet fail. Fail, meet irony.

Indeed.

If you don't want your luggage inspected, check a firearm. The TSA is not supposed to open such cases (declared as containing a firearm).

And if the owner happened to choose to protect the firearm in the shipping container by use of padding made of green cotton/linen paper, that Locked Box on a domestic flight TSA cannot open might contain a few hundred thousand dollars. . .oh, wait, that would be legal. Sorry TSO, no Big Catch™ today.

Must type fast. Head is about to explode. Cannot compute.

So declare a gun, TSA can't open the luggage for inspection, does it fly or does it get yanked from the luggage? What if you declare a gun so as to have secure luggage and have no gun in that luggage? Does that fall under another obscure paragraph that causes another forfeiture of $$$$?

Dean, does anyone writing the rules ever bother to talk to anyone else about the rules before the rules get implemented? I mean in cases like this a sanity check would be great.

Before I go buy a pellet gun, would anyone who routinely flies with firearms in checked baggage confirm this? Thx.

However, I have witnessed, on my last two occasions of flying out of FLL, TSA personnel requiring pax to open the locked gun case at the counter to validate contents prior to going down the luggage chute to the inspection area.

I think its the gun case itself that is locked/protected not the entire bag ... so yes, that means with the unlocked/tsa lock bs, etc that potentially the bag is later opened and the case removed ... How is that handled now?

AFAIK, gun cases are not permitted inside of other luggage. I always thought gun cases used for transporting weapons as checked luggage are supposed to be hard-sided cases and checked with the airline as individual pieces of luggage.

Man. When Dean said "guess what?" I was hoping it would be something cool, like the war on water being repealed

I've had a weapon inside of a locked Pelican Case that was inside of my normal luggage. No problem at all.

As I recall, weapon's cases aren't the only thing that the TSA isn't allowed to search. I believe that they also cannot search a packed parachute that is checked in as luggage.

There is always a first time when TSO training is involved...

Kind of. Since actually opening it for inspection would destroy its usefulness as a parachute (so says a basejumper friend of mine; something about some kind of release charge or something that has to be triggered to get it unpacked, and costing about $60 to replace it after screening) any need to actually screen the thing requires that we (a) have the passenger come and do the actual opening of the parachute, and (b) have the passenger's explicit permission to screen it.

If the passenger does not give explicit permission to screen it, however, then it will not be allowed to go anywhere except back outside of the airport.

TSA's guidelines for traveling with parachutes.

The same guidelines exist for chemical protection suits that the Army (or whomever) might bring through the checkpoint. If a need to search it arises, the passenger has to give explicit consent (since opening it for inspection would de-sterilize it, or something~). If the consent isn't given, then the item is denied entry into the sterile area, or denied carriage in checked baggage (whichever applies).

No, you can have handgun cases inside of other bags. The only really major difference is that the declaration form needs to be outside of the handgun case - like on top of it, or whatever - instead of inside of the case itself. Otherwise, everything else still applies: needs to be hard-sided, needs to be locked (and, apparently, without the lock being a TSA-Approved lock).

Everything else being said--
--is incorrect. As GoingAway has stated:

(to answer the question at the end - we screen around the handgun case inside of the suitcase)

It is the gun case itself, not the entire bag that the gun case is in. Some FSDs (such as the one in HSV) have still mandated that, at their airports, the interior of the cases will be inspected. Really, the "don't open gun cases" thing was directed at airports that used the big CTX x-ray devices in baggage. In that case, you wouldn't need to open it unless there was something else inside of the bag that warranted inspection. But as for the scenario of having a big, massive Pelican case with a starter pistol declared and sitting on top of everything else - no. Declaration of a firearm is not a "get out of screening free" card.

TSA's guidelines for traveling with declared firearms. You will note the fifth bullet that states the case might need to be opened. There's also that very last sentence, too - "TSA locks are not approved for securing firearms." - that I don't think was on there the last time I actually looked at the page.

Sometimes, I wonder. From what I understand, this was an FAA thing (and, apparently, from a very, very long time ago) meant for the airline side of operations, not for screening. Which is probably why things have been chuggin' along just fine for the past five and a half-to-six years (or so; whenever the TSA locks got introduced) with TSA locks on gun cases, and nobody bothering to notice. The airlines didn't seem to care, and TSA didn't seem to know. Well, somehow or another, somebody now made TSA aware of it.

Or so it seems.

There go my plans for securing the tool chest.

There, there. /shoulderpat

Are you flying out of FLL in DL terminal 2? I know where TSA is behind the door near the larger oversized belt. I remember that I realize know TSA is sitting in the chair wait for more larger equipment need to be searches. So when the bags is cleared. He will put into the conveyer belt. It will send downstairs instead of going to x-ray machines room.