You can't learn this blueprint. The row marks the M249 not researchable, so every one on a server came out of a crate, as its item page says, and the calculator prices what you carry onto a roof: a rifle body, a heap of gears and springs, and a good pile of HQM.
So keep it, and keep it alive. A belt-fed gun that holds the roof through an online raid is worth more than its parts, and a repair bench tops it up for a share of the metal, never a new body.
The recycler only makes sense for one nobody will fire. The ordinary one returns all the gears and springs an HMLMG needs and most of its HQM, with the body on a coin toss. If your group has that blueprint and no one wants to carry an M249, the trade turns a loot gun into one you can rebuild.
Questions
M249 ×10: how many resources?
High Quality Metal ×400, Gears ×60, Metal Spring ×60, Rifle Body ×10.
