I can't really answer your questions with any sort of personal experience, but go over to
www.marineocs.com , and specifically this thread
http://www.marineocs.com/portal/modules.php?name=Forums&file=viewtopic&t=193
As promised, here are a few negatives about being an enlisted Marine before attending OCS (The 7 positive things are also in this thread if you missed them, but you have to look at topics from the last 2 weeks). Coming up with this list was a lot harder because since I am going the enlisted to officer route I am a bit biased.
1. The possibility of deployment. As a cantidate you are complete nondeployable until you are commissioned. If you are enlisted and you get activated for deployment, you finish out the semester and you are either fast-tracked to MOS school (if you are a 92-day reservist) and then Iraq. Or you leave with your unit and go to Iraq. The Marine Corps. has 7 month deployments, so you'd only miss one semester of school, but it is still something you should be aware of.
2. *Unable to change your mind. If you attend OCS and decide it's not for you, then you can DOR and never look twice at the military. If you are enlisted and you make this decision, your best bet is to just serve out your time and not re-enlist.
3. *Time committment. There are several ways to become enlisted before attending OCS. The most popular is to become a 92-day reservist. Basically, you split your training up and do boot camp one summer, MOS school the next, and MCT the final summer. The problem is that MOS school and Boot Camp take up alot of time, so two summers are pretty much gone as far as internships and summer classes go.
4. *Limited choice of MOS. If you choose to go the 92-day reservist route, then their are certain things you have to take into account. One of them is the length of MOS school. You are able to choose MOS available in the Marine Corps., but the school is longer than your summer break, you have to either A) choose another one or B) miss a semester of college.
5. *Limited choice of MOS. Another thing you have to worry about as a 92-day reservist is where your reserve unit is located in relation to your school. Each reserve unit only harbors so many MOS slots. If you don't make sure that the unit you get assisgned (and you have a lot of choice in this) is close to your college, then you could be in for alot of travel expenses.
6. *Attending drill. I really don't think of this as a negative, but it is something that you should consider. As a reservist, you are expected to attend drill once a month. What you do at drill varies depending on the unit. Speaking from experience, you may spend one weekend doing PT and field ops all drill period and spend the next one standing around waiting for a change of command ceremony. Drill itself is fun, but you have to remember that drill is not based on your schedule. As a result, their will be times when you have to miss a party, or a family function, or have a hell of time studying for some exam because you have to attend drill. Units are fairly flexible about letting Marines make up drill time at their convenience if something serious comes up (final exams, funerals, class trips etc.), but it is still something to consider.
7. You have to deal with jerk-off OCS cantidates who think they're locked-on because they attended PLC jrs. and have read a few things about the Marine Corps. Seriously, do not forget that until you get commissioned YOU ARE NOT MARINES!!!
* 3-5 aren't that big of a deal. They just require appropriate attention to detail on the part of the cantidate. 6 can be a bit of a downer, but I've never had drill interfere with anything important, and like I said your unit is more than willing to let you make up the time if you absolutely can't drill that weekend.
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