Hail Mary is a Catholic prayer asking for the intercession of the Virgin Mary. From this we get the Hail Mary pass which is a desperation long pass at the end of a football game with little chance of success. Now let's try to define the Hail Mary bankroll in blackjack. The term "little chance of success" seems very subjective. I think a more mathematical or objective definition is available. Hail Mary Blackjack Bankroll Defined: A bank being bet in such a way that in the long run will experience negative or no growth. Examples: Fixed bets betting 50% or higher ror. or Resizing bets betting 2 * Kelly or higher. The above are formulas for bankroll disaster, for bankroll success one needs to bet far less. Given the definition it seems the Hail Mary Bankroll is not a sound choice, in blackjack the game never ends!