Do I have to keep my old MOS when going back into the Army?

They'll give you whatever they have a need for at the time. You get to pick, but it's not necessarily the choices you want.

It all depends on the HRC prior service business rules that are constantly changing. They are primarily based on what are the needs of the Army. The Army kinda sees it like you were in, you thought you could do better getting out, now you want back in, Well now the shoe is on the other foot.

Most MEPS will try to put you back into your old MOS, it costs a significant amount of money to re-train a Soldier let alone a prior service one. The CSM is right, needs of the Army will be the priority, you have to ask yourself “Why” are you going back in? Do you want to work the system and try to reclassify? Do you have the Line Scores on your ASVAB to serve as a 35F? What was your GT Score? ST score?

I had a five year break when I came back in. I was a 12B and was sent directly to A.I.T to reclass. So, unless something has changed, it's completely possible.

This is truly a question for your recruiter. There are a few variables that prevents anyone from giving you a difinative response, active duty, reserve or guard? It will also be determined by Army end strengths. So call you recruiter and test them by calling another.

Short answer is no. You can reclassify as a “will train” if the unit has slots and will accept you.

However - big however - the clearance process needed to perform that MOS is very lengthy and expensive, so those slots are very hard to come by

This depends on a few things.
1. Your test scores.
2. Can you get a clearance.
3. How much BS the recruiter give you telling you you can't change MOS or you have to pick something you don't want.

It will be tied to your grade determination. They give you a list and you pick. It may even be one job choice and a choice of assignment, or one job choice. We had a lot of people with one or no choices. E4 and below will be more. Not sure if they are currently taking NCOs. Pretty fluid stuff day to day and week to week to fill schoolhouse seats/unit needs.

You can if it's available. I got out as a 25u and was able to go back in 8 yrs later as a 19k

Having done this myself, I agree short answer is no you do not have to go in as same MOS. Will MEPs try to sell you on it? YUP! So the question is really how bad do you want back in and are you willing to go same MOS? If you do, there is always a chance to reclass during your re-enlistment window, but what you want might not be available. I was out for 7 years and there was no way I wanted to be ammunition again in Army. I wanted 15R Apache Attack Helicopter Repairer. They wanted me to go in as a COOK!!!!! Because I was a restaurant manager, Are you kidding me??? I told them to kick boots and I was going home. Told me to go have some lunch and come back in like 30 mins.....when I did, the supposed 15R position that "didn't" exist prior to lunch, appeared before my own eyes. So I got what I wanted.....is this typical I doubt it, but it all comes down to what you feel comfortable doing. If you just want back in, then take what you can get.....if there is principle involved like with me, stand your ground. Lets be honest, there is a need in a lot of MOSs some more than others. And at the end of the day we are not making our mission in recruiting as a whole.