would a charge of 265 15a/a be correct if the victim was not 65 or older. Shouldnt the correct charge be 265 b or c?

MGL 265 § 15A involves an assault and battery on a person who is 60 years of age or older, not 65 as asked in the question.  If the person is less than 60 years old, the case could be dismissed; but, in all likelihood the Commonwealth would amend the complaint to Assault and Battery by means of a Dangerous Weapon per MGL 265 § 15A paragraph b or c. If the case were dismissed, it would be dismissed without prejudice and the Commonwealth would refile the complaint.   You should contact an experienced criminal attorney.  The attorney could attempt to negotiate any amendment to the complaint to a misdemeanor charge, not a felony, as currently charged.