USMC MOS selection question?

I'm thinking of enlisting in about a year or so and was wondering if I can get 0311 in a contract rather than 03xx. I just want to know if I go into a recruiting office and talk to the recruiter about taking the ASVAB. Once I get my score in the ASVAB I want to know if I can just outright tell the recruiter I want the MOS 0311. I've been told the recruiters will try and sign you for other MOS's so I should just walk into the office and demand the MOS I want as long as I'm qualified for it. Since I don't think I'll have a problem scoring atleast 80 on the ASVAB should and can I just tell the recruiter I will not enlist unless I am 100% guaranteed the 0311 MOS?