Aerokroil is the best on rusted and seized items along with PB blaster, pretty hard core on the nose and skin.
WD40 is a great preservative and a fair penetrating oil.
Cheap to use on guns and wipes off to a tolerable coating.
I use Zepreserve for water displacement on ignition components. I am a mechanic. Will work for Ammo.
try Sea Foam Deep Creep. I’m a plumber by trade also HVAC/boilers (50 years just retired not long ago) and years ago we started carrying Deep Creep on our trucks. Works great on rusted pipe fittings, best thing we’ve used. Especially on boilers. Unless you can use a torch of course. I use it on my cars as well.
For cast iron pipes that wont come loose.... an apprentice and a sledge hammer work best.
Never heard of that one but put it on the Amazon wishlist to remember it. Learned a lot on this thread.