If successful, the technology will be owned by the arms dealer, but the US military will also keep the technical information and have the right to use this technology (but it will definitely pay the patent).
The R&D project must be funded by itself at the initial stage. Whether the federal government gives funds mainly depends on the R&D cycle and project plan. Let me give you a simple example. SCAR special assault rifle is a weapon plan proposed by the United States. This scheme finally adopts MK 16 of FN. Because firearms are products with short R&D cycle, they have been perfected after R&D has won the bid, so you can pay for them only by placing an order without mentioning it again. The Comanche project you mentioned experienced a long follow-up research and development work after winning the bid, during which the research and development funds were provided by the US military.
As for why arms dealers should listen to the United States, it is because, first, the US military is their food and clothing parents. In all aspects, first, the largest customer of American arms dealers is the US military. Second, any export trade must abide by national laws. After any weapon is developed, it is necessary to sign an agreement with the military to clarify which party can sell and which party cannot. The U.S. government is stuck at both ends by arms dealers, so American local arms dealers have always listened to the U.S. government.
As for privatization and freedom of buying and selling, the United States is a country ruled by law, and the basis of freedom is law-abiding, so is private ownership. The U.S. military signed an agreement to use your technology, and it is not without money.