All the big projects force the big guys to subcontract to smaller companies
The problem is actually completely different:
There is no way for a "little guy" to become a midsized company b/c the government is completely incompetent and relies on the huge defense contractors for guidance. The gov't has VERY little internal expertise - so if you have a brilliant new idea that is perfect for a midsized company to execute (which will often have to be on an existing platform built by one of the big companies) they have to go to the big companies to see if it's feasible. The big companies ofcourse say it's impossible and then (if it actually was a good idea) they steal the idea and implement it themselves.
So unless you can go from doing SBIRs (ie. under 200 employees) to build a whole tank on your own - you're fucked