Note it doesn't matter what sentence is actually imposed, it's based on the MAXIMUM punishment the court *COULD* have imposed. Maximum permissible punishment is based on the offense, and the type of court-martial. The maximum prison-term which can be adjudged by a Summary court-martial is 30 days, regardless of the offense. Special court-martials can impose sentenances up up to one year, but prior to May 2002, Special court-martials were limited to imposing sentances no greater than six months. General court-martials can impose any sentance, up to the maximum punishment listed for the particular offense in the Manual for Courts-Martial (MCM).
So, those convicted by a Summary court-martial, and those convicted by a Special court-martial, prior to May 2002, are not considered to have a "felony conviction."
For those convicted by a General court-martial, or a Special court-martial (May 2002 and later) may have a "felony conviction," depending on the maximum punishment authorized for the offense, under the MCM.
For more information about court-martials, see our Military Justice 101 article, Part 7.