Ley Federal de Armas y Explosivos
Pursuant to Mexico's Federal Law of Firearms and Explosives:
http://www.natlaw.com/trans/tnstcs1.htm
Arms are prohibited by specific caliber. The FLFE provides:
ARTICLE 11: The weapons, ammunition and materials for the sole use of the Army, Navy, and Air Force are the following:
b) 9 mm. Parabellum, Luger and similar pistols, .38" Super and Commando pistols and those of larger caliber than these.
What this means is that the only 9mm caliber prohibited is the 9x19, which we understand to be 9mm, 9mil, 9 milimeter, etc. Article 11 DOES NOT prohibit 9x17, .380, 9x18 Markarov, etc. It specifically names 9mm. As for size of caliber, that is also a bit of a misnomer as the prohibited calibers refer either to diameter or enumeration/name. For example, .357 magnum is an enumerated round but is also the same "caliber" or diameter as .38 special which IS legal under Article 9 below. Though both are .38 or .357 only .357 magnum is barred.
Thus, .357 Sig would be the proper diameter AND is not one of the named/enumerated prohibited calibers.
The following calibers are allowed under FLFE:
ARTICLE 9th: According to the terms and limitations set by this Law, the following weapons may be possessed or carried:
l. Semi-automatic pistols of greater than .380" (9 mm.) caliber, with the exception of .38" Super and .38" Commando pistols, as well as similar models of other brands, of the same caliber.
2. Revolvers of caliber not greater than the .38" Special, with the exception of the .357" Magnum.
Article 9 read along with Article 11 means hat any caliber "larger" than 9x17 (.380) is legal, except for 9mm parabellum (9x19). As mentioned above 9x18 Makarov is not on the list.
Now, turning to all of the calibers not on the list:
.17 Mach. Imagine this tiny little bullet in FMJ,
http://www.handgunsmag.com/accessories/mach2_101204/ . Nice little pistol caliber.
.22 Magnum. Clearly, this round is smaller than .38 or .380, and it packs a lot of sting.
http://www.gunblast.com/AMT-AutoMagII.htm
.32 ACP. Ah, a classic. It has it's own place in history and its own pop in a little package.
9x18 Makarov. It is not 9mm parabellum, Luger, etc. It passes.
.
25 NAA. A lot of zip in a tiny hand held pistol,
http://www.naaminis.com/25NAArel.html
.32 NAA. A bottle- necked bit of trouble,
http://www.naaminis.com/32NAA.html
.30 Luger. Yes, .30 Luger! That under-appreciated round. Recall that the Hi Power in .30 Luger was made specifically for countries that banned the 9mm parabellum. The .30 Luger is a hot botte necked bullet.
5.7x28 mm. The FN Five Seven fires this devastating little miniaturita of a round,
http://remtek.com/arms/fn/57/. And it is legal under the plain terms of the above laws.
.357 Sig. It is clearly not the enumerated .357 magnum. Nor is it the enumerated 9mm Parabellum, Luge, etc. It is however approximately the same diameter projectile as .380 or 9x17 mm. Until the Mexican legislature enumerates this round, it is good to go.
7.62 x 25 mm Tokarev. Clearly the caliber is smaller in diameter than any 9mm. This is an extremely powerful round.
This should be plenty of pólvora (firepower) to keep malhechores (wrongdoers) acting under color of law or not at bay.
Folks, feel free to chime in with any other calibers not on the list .25, .30, .32, 5mm, 6mm, 7mm, 8mm calibers for auto pistols.
Enjoy