FAP and direct ascensions are subject to the particular service deciding they need more physicians in that specialty that year.
It's possible that some years the service will determine it's overmanned with internists and offer zero FAP spots to internists in training that year. Historically this process hasn't been very transparent or easy to predict.
In general, military medicine is a small numbers game that lends itself to a lot of year-to-year variability and uncertainty regarding the competitiveness of in service residencies or FAP availability. It's hard to give you a meaningful "how competitive" answer.
It might be easy, it might be impossible.
