@nugger @RegalBeagle @Bad_Banner @IAMAL_PHARIUS @TrevorGoodchild Yeah, you're correct.
But this sector in particular the training is complicated as comes with extras not many are aware of.
You can't effectively train people until you bring them in, many are offered apprenticeship or stages in smaller companies, to familiarize with the basis of the machinery until eventually moving up the ladder into bigger companies with major responsabilities, for which they'll have to be deeply screened and vetted.
Smaller companies and subcontractors are the industry's gatekeepers.
Anyway, even to produce simple 155mm artillery shells (as finished product) you have to be vetted from the big eye, this means that factories are often understaffed (euphemism).
Don't get me started on tank's armor specifics or system's electronics, those who produce export-able products (or licensed) and those who produce the full system are on a different plan.
Obviously the latter pays better, if you can get in.
But still, is harder to move or swap entire productions with short notice, so you're, as a company, stuck with your base configuration until your laborers are allowed into the next security level to begin working on the new project, or forced to headhunt for already vetted personnel.
This process, alone, lasts months.