Obviously you lose your rights while in prison --- but if you are considered not a threat to society and can be set free then you should have your rights. A lot of crimes fall under the label "felony". If you're going to murder, you can obtain the means to do it --- but if that's the case, you should stay locked up.
If you've served your time, are elgible to vote and have not been adjudicated a violent offender, mentally incompetent or an addict I think you have the right to purchase and own firearms. Regards