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Automatic Winner Charlie Rule in Blackjack
Rarely in blackjack there is a rule that if the player reaches a certain number of cards, usually 5 to 7, without busting, the player will automatically win. This is called a "Charlie." If the player automatically wins with 7 cards or less, without busting, that rule would be called a "seven-card Charlie."
As shown in my blackjack section, the house edge is lowered 0.01% under the seven-card Charlie rule, 0.16% under a six-card Charlie rule, and 1.46% under a five-card Charlie rule.
The following table shows the strategy for hitting, standing, and doubling. This differs slightly from the Charlie strategy in Basic Blackjack by Stanford Wong. The strategy below is based on an infinite deck, and thus may be wrong in some borderline situations. If you have Wong's book, I would defer to his strategy.
The next image shows the splitting strategy, which depends on whether or not double after a split is allowed, and whether a five-card or six-card Charlie rule is in effect. There should be no changes for a seven-card Charlie. Again, this is a little different from Wong's strategy, which I defer to.