[Blood of Tyrants]

mamelukesabre is right. You can manufacture your own firearm as long as you never transfer it to another person.

[FLAMING DEATH]

Actually, you CAN sell your privately made gun, as long as you didn’t make it expressly to sell.

There’s a lot of gray area, but many recommend that you only manufacture one at a time and keep them for at least a year.

That will supposedly establish that you are not manufacturing to sell.

[Trailerpark Badass]

Actually that is not correct. You may sell personally made guns.

You just cannot make guns with the intent to sell. That requires a license.

Which is what it appears this person is doing.