Getting your FFL-31-SOT is pretty easy. It's just some paperwork. The tricky part is the taxes and license fees; which are admittedly pretty stupidly high. IIRC they're somewhere in the range of 4 digits - 5 digits.

using what the ATF classifies as "Destructive Devices" (40mm grenades, mortars, etc) requires tax stamps still, and some paperwork, registering who has it and where it is, etc... but they are legal.

If you're a convicted Federal Felon who has served their sentence, you can petition the courts to have your right to possess firearms reinstated. Of those who petition, most get their right reinstated; in the pro-gun areas. You only get one shot though IIRC; so you should go to a court in a heavily red state to have the best chance. It's a federal-level decision, so pretty much any federal court should do.

With the way the current administration is going; as much as I disagree with some of their decisions, the NFA is well and truly on its way to the grave.

Every law abiding citizen should be able to possess and operate any firearm, regardless of fire rate, caliber, or form factor.

Good luck, brother.