That's only 1400 that we know of. Were there operations in NM, CA, TX? I doubt the DoJ, ATF, FBI, DEA, CIA are going to volunteer that information.
I see these investigations as being in the early stages. We can look forward to many new revelations as the days go by. But 1,400 rifles “walking” around Mexico should be more than enough to have a few more turn up at some fresh murder scenes. It’s not like the cartel’s killers are shy about using them.