How difficult is it to switch from Army Reserve to Active Army? Specifically for a 17C?

Yes, you’ll be governed by the prior service business rules. You can find those on the goarmy.com website. It’ll have the mos that the Army is looking for broken down by grade.

SGT (Join to see) "Back in the day" 1969-71 there was. My Unit promised me a rank increase tp SPC-4 if we came out number 1 in the Motorpool paperwork inspection. We did... but they didn't. Since I levied 11B to Vietnam they didn't want to "waste" the promotion on me. The SPC-4 that was promised E-5 didn't get his promotion either... he was ETS'ing shortly.

You Need to talk to a Army Recruiter. It is a simple process not difficult to complete if everything works perfectly.

Step 1: Army Recruiting gives you Conditional Relase Form

Step 2: Submit Release form to Unit let it works way up Chain to get signed off on (Hardest Part multiple factors go into this)

Step 3: Once released you will be considered prior service applicant so you would have to be within the those MOS(Recruiter will have information)

Most important step is go in to a recruiting office and explain intentions