I don't know that for a fact. It could be so. Aero Precision is a Space and Aeronautical parts builder and has contracts with NASA and other aircraft manufactures. I would make sense that they would branch out and make lowers to other vendors specs. They would have a heap of CNC machines so keeping them all working would make for good business practice. Spikes is solid kit to a point I can't deny that. They look and feel better than Anderson but they make their own receivers as well ( anderson does ). I don't consider Aero low line kit ( kind of mid-mid line ) but I wan't something a little unique.
As far as I know there is only one manufacturer that makes every part on an AR down to the detents and that is Daniel Defense. However like someone said in a earlier post finding a DD lower is like finding a sparkling red diamond. Now that they are making their own parts they are leaning towards being able to work and repair all the machines that make all of their parts. Other from their facility in Georgia they have also acquired a 12,000 sq. ft. facility in one of Carolinas as well. Also built two large add ons in their Georgia plant.
It's hard to tell who is making their parts these days. Other that ones I listed I couldn't tell who's making who's parts. The only one's I know that make their own receivers is, Stag arms, Aero, Anderson, Daniel Defense, Mega and that's all I know of. I am sure their are small really unique billet makers that have a couple of CNC machines and make their own receivers but I couldn't be for sure who those are.