Several years ago I bought a 26.5 mm Model VZ44 Czech Polish Flare Gun. I seem to recall it was about fifty bucks. It was in nice shape and did not require an FFL. I also acquired an insert tube so it will fire the .12 gauge flare which is suitable for the less expensive flares you can find in Walmart. It is not suitable for .12 gauge shotgun shells. I do have some of the correct 26.5 mm parachute flares, but they are expensive.
As time went on I acquired both the .22 sub-caliber insert barrel and the .410/.45 Colt insert barrel. Once you stick either of these sub-caliber insert barrels, then by law it must be considered a firearm. None of these sub-caliber inserts require and FFL. Therefore, it is possible to end up with a firearm and never have to undergo a background check. It is a single shot and probably not much of a terror threat.
Shooting the flares are nice and great for the 4th of July. I do live on a large lake, so they can be carried if needed on my boats.
I think there is also a .38 Special sub-caliber insert available on the market.
The .22 sub-caliber insert works pretty good an reasonably accurate; although the flare gun has no sights. Firing the .410 gives a pretty good spread at about 15 yards, and the pattern is not bad. The .45 Colt rounds tumble and put some pretty nasty holes in the target paper.
The recoil is not bad. I am not a prepper and think there are better choices for a survivalist or prepper. In my opinion, the best round would be the 3 inch .410 for snakes and small game.