WITH FEW EXCEPTIONS, THE MARINES DON"T GUARANTEE AN MOS
When you sign your enlistment contract, you can select a particular occupational field such as Infantry or Engineering.
In some unique cases, you can sign for an MOS such as Enlisted Musician or Reconnaissance Marine.
If you don't sign for an occupational field or MOS, you'll go open contract. This means you can be selected for any MOS in the Marine Corps that you have qualified for.
HOW DO I SELECT AN MOS?
Candidates for enlistment will first have to choose which Enlistment Contract they sign before being assigned an MOS by the Marine Corps. The contract they sign will play the most important role towards ensuring getting an MOS (essentially a career specialty) you want. Each contract has either one or many MOS's under it.
Contracts available to a prospect will be based on their ASVAB scores and the Needs of the Marine Corps.
Marine Corps manpower planners look at forecasts of future force numbers and decide how many of each contract will be required in a given fiscal year - hence Needs of the Marine Corps.
Needs are based on the size of an MOS field. Some MOS's such as infantry are large in contrast to the small musician field.
Candidates have very little, if any influence on this factor, but the Recruiter will provide the candidate with a list of options which they qualify for based on their ASVAB scores and what the Corps has available at that time.
WHAT IS AN OPEN CONTRACT
A poolee or recruit who holds an open contract can be considered a gambler putting everything on a roll of the dice. They can be assigned any MOS for which they are eligible for.
Candidates for enlistment who choose this route often seek to ship to Recruit Training at the earliest opportunity, so they will not have an MOS prior to shipping boot camp.
Though the individual's ASVAB score will still weigh into the selection, the ultimate decision for an MOS will be completely at the discretion of the Marine Corps' needs as we discussed before.
In this case however, an Open Contact individual will not know their MOS until late in Recruit Training.
They will not receive a list of options to choose from, but instead they will only receive a notification from their training staff what their occupation will be.