It's actually more complicated than that. In many states if you are convicted of a non-violent felony then at the end of your sentence your firearm rights are automatically restored. There are also the cases of pardons, expungements, and other restorations of civil rights. It varies by state, and while USC 922(g) outlaws firearm ownership possession by any felon, in practice the Federal courts look at whether the person has had their civil rights restored in the state of the alleged offense. When it comes to Federal charges, the prospect of amelioration is grim. In the Federal scenario, there is no expungement or pathway to restore your civil rights, but a pardon is possible. [0]

There's also a discussion to be had about your and the legal definition of a "gun." For example, antique firearms such as some black powder rifles are specifically excepted [1] from the Federal legislation, but it could vary on a state by state basis.

[0] https://www.justice.gov/archives/jm/criminal-resource-manual...

[1] https://www.law.cornell.edu/uscode/text/18/921

Well they can, they just aren't allowed to...