Concur with slashsplat. I spent a career as a professional buyer, with a focus in aerospace, in which end user was US military. Engineering drawings are very specific and lot variance (within or without sole source consideration), was always a big deal.
I just saw a Modern Marvel episode in which carbon fiber was featured. While I understand the diversion of CF for military and commercial airlines, it is still available. The R9 is not a cheap gun to begin with and G10 has all the charm of gun laws in New Jersey.