Re: Castillo de San Marcos, it's this one:
In November of 1702, the British laid siege to the city. All of the city's residents, some 1,200 people, along with all of the fort's soldiers, some 300, remained protected inside the wall of the fort for the next two months during the siege.
I think if they can fit 1,500 people in there then we should safely be able to maintain about 500 or so with room to spare.
After the siege of 1702, the Castillo underwent a period of reconstruction. Beginning in 1738, under the supervision of Spanish engineer Pedro Ruiz de Olano, the interior of the fort was redesigned and rebuilt. Interior rooms were made deeper, and vaulted ceilings replaced the original wooden ones.
The new ceilings required the height of the exterior wall to be increased from 26 to 33 feet
Proximity to the "Voodoun" lands do not make this exact location to be a good option, however as an example of how to build, it does stand the quality test.
My suggestion is to use this as a template with a modification for a larger size (it only takes up about 2.5 acres total... see this next photo with vehicles for scale)
I would expand it to encompass approximately 4 to 5 acres & possibly add Mac's Flak Towers... here's a variation on the design:
I think square is better than round or maybe even an x or + pattern works best like in the Spanish fort because you get cover fire the supporting parapets.
Clever wants one (one "something") somewhere within 200 miles of Austin & I am a fan of a relatively close safety location, however I do think a cold weather final destination should be discussed. Should we look to establish a chain of smaller fortresses along the way?
As to the .22 LR shown, I am not quite so much a fan of the tube feed loading as it's only going to give you around 17 shots before you run out & they are NOT easy to load under time pressures. If you go with the tube feed method, you'll need powder monkeys on hand & I'd rather they be shooting most of the time, not loading.
In stead, might I suggest a clip feed style magazine?
Take THIS:
& you can rapidly feed THIS:
You can even clip them together like THIS:
Each clip holds 30 rounds, so 90 will get you pretty far.
Looks to me like our solution for rifled armaments has narrowed down a bit.