I was there a while ago - it's a fun place and for a few dollars you can take an AK out behind the shack and let rip. Usually the tourists use Russian ones and they are less likely to explode on you than the local copies.
I saw him thread a muzzle and priming rounds. It looks very much like they are getting 99% done guns and just assembling them, or making stocks or converting them to select fire, which happens in Mexico already. That's just a technical redefinition of what a "gun" is. However even if Mexico was forced to make do entirely with 90% lowers, it would still be a massive restriction in volume. The number of lowers is way, way smaller than the number of guns that are made every day.
http://www.mirror.co.uk/news/world-news/town-ak-47-sells-les...
I was there a while ago - it's a fun place and for a few dollars you can take an AK out behind the shack and let rip. Usually the tourists use Russian ones and they are less likely to explode on you than the local copies.