12 Gauge From Hell
The 12 Gauge From Hell (12 FH) is a wildcat cartridge based on various sizes of 12 gauge shot shell. Certain loads have been known to achieve terminal ballistic performance greater than that of the infamous .50 BMG, and unlike most other cartridges with a bullet diameter greater than .5 inches, does not qualify as a Destructive Device under the NFA. Additionally, unlike many other rounds larger than and including .50 BMG, it is legal in all 50 states, even for hunting.

The average person will likely need a brief introduction to certain topics, to include the "gauge" system of measurement, shotgun cartridge sizes, some basic related terminology, and a brief history on wildcatting.

What is gauge, and how is it measured?
Gauge is a measurement used almost exclusively for shotguns. It is sometimes used for very large big-game rifles, where it is also known as a bore number, for example, a 4 bore is the same as a 4 gauge. It is also the unit of measure on antique cannon and artillery.

The gauge of a barrel is the multiplicative inverse of the weight, in pounds, of a sphere of pure lead that would perfectly fit the interior diameter. Put more simply, a lead sphere weighing 1/12 of a pound would fit the inside of a 12 gauge barrel, a 1/20 lb. sphere would fit a 20 gauge barrel, and so on.

While gauge technically only defines the barrel's interior diameter, shotgun shells are chambered to standards across the board based on gauge and length. A chamber (and therefore cartridge length) of 2 3/4 inches is the most common size of shot shell, though today 3 inch ("Magnum") are common, and 3.5 inch (Supermagnum) are the largest current commercial offerings.

It is important to note that a shorter shell can be chambered and fired safely from a longer chamber of the same gauge, but the reverse is not the same.

12 gauge is by far the most common today, though 16 and 20 are not unheard of; 10 gauge, once common, has been almost entirely superseded by modern 12 ga. 3" magnum shells.

What is "wildcatting"?
Wildcatting is the niche practice of designing a new, custom cartridge specification that is not mass produced. Wildcats are usually based on an existing, usually commercially produced cartridge, and sometimes later put into mass production if it is adopted by major manufacturers.

It can be as simple as using a different, usually more powerful propellant charge, as is the relationship between the wildcat .45 Super and the standard .45 ACP, or a radical alteration of the dimensions, as is the case with the .22 Eargesplitten Loudenboomer - a .378 Weatherby Magnum cartridge necked down to carry a .224 bullet.

Origins of the 12 Gauge From Hell
Originally developed by two high caliber rifle enthusiasts as a much cheaper alternative to other large caliber wildcat cartridges, like the .600 and .700 Nitro Express, or the .577 T-Rex, the 12 FH began getting major publicity among wildcat enthusiasts after initial development data was released on several Internet forums. The chief developer posted a few photos and some explanations, and followed with a steady, if slow, stream of notes over the next several years.

He chronicled everything from load development to the building and modification of several firearms to shoot it with. The original 12 FH cartridges were made by removing the neck from .50 BMG brass, machining threads onto the base, and fitting a separately manufactured rim to make it extractable from 12 gauge chambers. Initially requiring nearly custom builds in hand-made barrels and chambers, as the design settled it became feasible to purchase and modify a New England Firearms 12 Gauge "Super Slugger" for under $500 total.

Several boutique manufacturers got onboard with the project, and now produce premade, one-piece brass shells designed specifically to load 12 FH. Complete load data is available for almost sixty loads, ranging from 3.5 inch shells designed to push an two ounce hardened lead slug at over 3000 FPS, to a 4 inch buckshot load designed for maximum shot volume.

For something resembling comparison; The "hottest" slug load reported for 12 FH is 850 grains @ 3000 fps - about 16,500 ft-lbs. - while a typical .50 BMG load is about 10,000 ft-lbs.

While still a boutique cartridge, it is not at all difficult, or even (relatively) expensive for the average person to acquire, load, and shoot. The developer of the cartridge has made inquiries directly to the BATF, and has received absolute confirmation that the 12 FH falls under the same exceptions to the Destructive Device regulations as does any other shotgun.

It is extremely important to note that it is absolutely not safe to fire 12 FH loads, even if they will fit, in any standard 12 gauge shotgun! Unless you can verify that the gun in question is rated for the pressures involved, you can easily wreck your gun, or kill or injure yourself or bystanders.

Mr. Hubel's initial post on The High Roads forums
Rocky Mountain Cartridge - Antique, custom, and special-order brass cartridges
12 FH at AmmoGuide - published load data for 12 FH

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