Q: What felonies would prevent me from getting an mhic license in Maryland

A: There is no list of disqualifying convictions. Rather, the applicant's specific circumstances, nature of the crime, age of the conviction, etc., are all considered to determine if the applicant meets the good "character" requirement. Here is the explanation given on the MHIC website:

"Each applicant is required to report to the Commission any conviction of a felony or a misdemeanor that is directly related to the fitness and qualifications of the applicant or licensee to engage in home improvement services. The applicant must provide a "true-test copy" from the clerk's office of the court where the conviction occurred. The facts the Commission shall consider in the denial, reprimand, renewal, suspension, or revocation of a license when an applicant or licensee is convicted of a felony or misdemeanor are: the nature of the crime; the relationship of the crime to the activities authorized by the license; with respect to a felony, the relevance of the conviction to the fitness and qualification of the applicant or licensee to provide home improvement services; the length of time since the conviction; and the behavior and activities of the applicant or licensee before and after the conviction."

Transportation of a handgun hardly seems relevant to any services or qualifications of a contractor performing home improvement services. I suppose if the crime involved threats of violence to others there could be a consumer citizen safety concern, but that would depend more on how you have lived your life since the conviction as a peaceable law abiding member of the community. I would stress the positive "behavior and activities of the applicant or licensee before and after the conviction" part of your history.