What is the biggest barriers for prior service members trying to join another branch of service?

especially if you have a break in service I would have to say lost records!!!!!

Recruiters not getting the points for recruiting prior service.

It completely depends on the people you know and what branch you are going to. As a NG member it took me maybe a month to finish the process to go active duty. but all of my higher ups were family friends and so my paperwork was fast. a friend of mine is still trying to go active from the guard and it has been over a year.