If these work in any AR10/M14 mags it would be 10s of 1000s. It would make good business sense for Magpul. Also, doesn't the US Military still use the M14 mags? It's a big market with no alternative like the AR15/M16 market that has the green followers.
Let see... large untapped market, strong demand, and virtually no competition. Doesn't take a Harvard MBA to see that this is a good business.