Pleas of the accused

(a) A plea of not guilty shall be entered in the record, and the court shall proceed as though an accused had pleaded not guilty if: (1) The accused after arraignment makes an irregular pleading; (2) The accused after a plea of guilty sets up matter inconsistent with the plea; (3) It appears that the accused has entered the plea of guilty improvidently or through a lack of understanding of its meaning and effect; or (4) The accused fails or refuses to plead. (b) With respect to any charge or specification to which a plea of guilty has been made by the accused and accepted by the military judge, a finding of guilty of the charge or specification may be entered immediately without vote. This finding shall constitute the finding of the court unless the plea of guilty is withdrawn before announcement of the sentence, in which event the proceedings shall continue as though the accused had pleaded not guilty. (c) A variance from the requirements of this section is harmless error if the variance does not materially prejudice the substantial rights of the accused.