Twice the length of Christopher's sword is 15 x 2 = <<15*2=30>>30 inches.
So, Jameson's sword is 30 + 3 = <<30+3=33>>33 inches long.
June's sword is 33 + 5 = <<33+5=38>>38 inches long.
Thus, June's sword is 38 - 15 = <<38-15=23>>23 inches longer than Christopher's sword.
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