Pardon the bump, it's still on the first page. I'm sure by now you have your answer, and personally even being on a first name basis with multiple FFLs type 10 I would still Form 1 an LMT M203 tube. Still, I hope you or someone finding this thread in the future finds this helpful.https://www.atf.gov/firearms/docs/undefined/0618-ffl-list-new-mexicotxt/download
I honestly thought there would be more like there are in PA. New Mexico has four FFL/10s and zero types 09 or 11:
DeGroat in Milan, Cibola County
Alliant Techsystems Operations LLC in Socorro, Socorro County
Energetic Materials Research & Test Center (EMRTC) in Socorro, Socorro County <--- doubt this one will transfer an LMT M203
6 Management Corporation in Alamogordo, Otero County
If licensed dealers/manufacturers/importers of firearms including destructive devices including armor piercing ammunition out west are anything like those back east most of them are contractors who won't give you the time of day.