The short answer is no. You cannot simply transfer. The Guards, Reserves, and Active Duty components are all different. With very few exceptions (mostly for medical professionals), one cannot simply transfer from the Reserves/Guard to active duty. One must get an approved discharge from the Reserve/Guard component., and then separately process for enlistment (or commission) for an active duty service. (Exception: Some Army Reserve and Army National Guard soldiers who are currently activated can apply for direct transfer to active duty.
However, one may apply to the Reserves and/or National Guard for a "conditional release." Basically, a "conditional release" says that the Reserve Component. or National Guard agrees to release you from the remainder of your commitment, if you are accepted for enlistment or appointment to an active duty service component.
To start the conditional release process, you must see an active duty recruiter. The Recruiter is the only person who can request a conditional release. He/she does this by submitting a DD Form 368, Request for Conditional Release. This form must be signed by the member and the active duty recruiter.
It's important to realize that a conditional release does not have to be approved. It's entirely up to the Guard/Reserve component. If your unit or component. is undermanned in your particular MOS/AFSC/Rating, they may disapprove the conditional release. It's also important to understand that this is not necessarily a fast process. I've known individuals who have waited for six months or longer for a conditional release to be processed. So, it's important that you allow plenty of time for the DD Form 368 to make it through the review process.
If the conditional release is approved, you may then enlist (through the active duty recruiter) as a "prior service candidate." (Or apply for OCS/OTS). This is true, unless you have not yet been to basic training as a Guard or Reservist. If you've not yet been through basic training, and you get a conditional release approved, normally you are enlisted active duty as a non-prior service candidate (which offers more enlistment options).
If your conditional release is approved, you will normally still be required to drill with your Guard/Reserve unit, until you actually go onto active duty.
Unfortunately, prior-service candidates are among the lowest on the recruiting priority totem pole. Recruiters do not get enlistment credit for enlisting prior service candidates (i.e., prior-service do not count against their recruiting quotas). Therefore, some recruiters are not all that excited about doing all of the paperwork (including the extra paperwork it requires for prior-service candidates) for a recruit they don't get credit for (Many recruiters would rather spend their very valuable time working with non-prior-service accessions because those recruits are counted against their enlistment quotas). For complete details, see Prior Service Enlistments.
Prior-service recruits don't get all the enlistment incentives available to non-prior-service applicants (Exception: Some services offer prior-service re-enlistment bonuses for prior-service who are already qualified in certain acute shortage jobs).
Usually, if a prior-service recruit has an MOS/AFSC/RATING that directly converts to an MOS/AFSC/RATING of the active duty service they are trying to enlist in, and if the service has a current need for personnel in that MOS/AFSC/RATING, then it is mandatory that the recruit enlist in that specific job. If the applicant is certified in a job that is not currently in need by the active duty service they are trying to join, or if they have a job that does not cross-relate to the service they are trying to join, only then may they enlist into a different job.
Conditional Releases are approved for a period of six months. If an extension is required, an additional three months may be granted. A copy of the Oath of Office or Enlistment contract should be returned to the losing component within the specified time frame.