Ok,I got this from Wikipedia.If it needs correction,don't shoot the messenger (pun intended
It is a bit confusing.
In regards to what type of firearms are permitted, Title II, Chapter I, Article 9 of the Federal Law of Firearms and Explosives states:
(translated) It may be kept or carried, under the terms and limitations established by this law, weapons of the following characteristics:
Semi-automatic handguns of caliber no greater than .380 (9mm Browning, 9mm Corto, 9mm Kurz, 9mm Short, and 9×17mm). Left excepted are calibers .38 Super and .38 commander, and also calibers 9mm. [Such as] Mauser, Luger, etc., as well as similar models of the same caliber of the excepted, from other brands.
Revolvers of calibers no greater than .38 Special, left excepted is caliber .357 magnum.
Land tenure owners, common land owners and farmworkers outside urban zones, may keep and carry, upon registration, one weapon of those already mentioned, or a .22 caliber rifle, or a shotgun of any caliber, except those of a barrel length shorter than 25 inches (635mm) and of caliber greater than 12-gauge (.729" or 18.5 MM).
Additionally, Article 10 of the Federal Law of Firearms and Explosives states:
(translated) The firearms that can be authorized to participants of shooting or hunting, to keep in their home or to carry with a license, are the following:
Semi-automatic handguns, revolvers and rifles of caliber .22, rimfire ammo
Handguns of .38 caliber for Olympic shooting or other competition
Shotguns in all their calibers and models, except those with a barrel length shorter than 25 inches, and calibers greater than 12-gauge.
Triple-barrel shotguns in the calibers authorized in the preceding section, with a barrel for metallic cartridges of different caliber.
High-powered rifles, of repeating or semi-automatic function, non-convertible to full-auto, with the exception of .30 caliber carbines, rifles, muskets and carbines caliber .223, 7 and 7.62mm, and Garand rifles caliber .30.
High-powered rifles of greater caliber than those mentioned in the previous section, with special permission for their use abroad, for hunting of game bigger than those present in national wildlife.
Under these two articles, private citizens are generally restricted to semi-automatic handguns or revolvers of a caliber no greater than .380 (for home defense), rifles no greater than .22, and shotguns no greater than a 12-gauge (hunting and shooting when a member of a club). Anything bigger than those calibers is considered for exclusive use of the military and strictly forbidden for civilian possession, as defined by Article 11 of the Federal Law of Firearms and Explosives. Only citizens with collector permits may be authorized to possess firearms outside those permitted for civilian ownership.