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Left to Right: 7mm Rem Ultra Mag Headstamp; The Wildcat, .284 Achilles; The Commercial Cartridges, .30-'06 Springfield and .308 Winchester

Wildcat is a vernacular term or jargon with two definitions; one provincial and the other commercial.

Provincial Terminology[]

In the shooting world a wildcat cartridge can be defined by one of three different criteria:

  • A cartridge not standardized by SAAMI or CIP
  • A non-standardized cartridge that cannot be chambered in any other chamber
  • A non-standardized Improved cartridge

The Wildcat Cartridge[]

The wildcat cartridge usually starts out as a military or commercial cartridge. There are an infinite number of reasons for wildcat cartridges, but usually the most basic reasons is to increase muzzle velocity or efficiency and/or caliber size. From these three reasons generally comes increased energy, better ballistics, accuracy, performance, and case life.

A wildcat starts with a parent case. Probably the most prolific parent case was the .375 H&H Magnum. Other parent case have been .300 H&H Magnum, 7mm Mauser, Springfield .30-'06, .404 Jeffrey, .300 Remington Ultra Mag and the .308 Winchester.

Typically when a designer wants greater muzzle velocity he goes for greater case capacity. This is done by pushing the shoulders forward, expanding the case walls, making the shoulder angle steeper and the neck shorter. Occasionally a designer increased case capacity by using “Basic” brass and using it at its longest length.

If you are after greater velocity as Roy Weatherby did in his first line of magnum cartridges, you start with the .300 H&H Magnum case. Change the interior dimensions of the chamber to meet the intended goals. Roy Weatherby not only pushed the shoulders forward and case wall outward to increase case capacity, he used a double radius “venturi” design for the shoulders. Part of Roy Weatherby's line of magnum cartridges still used the .300 H&H Magnum case. But instead of being full length (2.85 in [72.4mm]) he shortened the case (chamber design) to fit in a standard length action (2.545 in [64.64mm]).

Although many wildcatters have necked a parent case up and down to change the caliber, the most famous example was that of Layne Simpson's wildcatting of the 8mm Remington Magnum. Mr. Simpson necked the 8mm Remington Magnum up and down from .243 to .458 calibers. One of his wildcats was “tamed”. The tamed wildcat that he gets full credit for, is the 7mm Shooting Times Westerner. This cartridge is a 8mm Remington Magnum necked down to 7mm (.284 in) with no changes. Remington necked up the 8mm Remington Magnum to .416 (10.6mm) with no changes to create the .416 Remington Magnum.

If efficiency is the goal you can do what Dr. Lou Palmisano and Ferris Pindell did in the early 70s. Their theory was that a small primer and short charge column was more efficient and therefore more consistent. Consistency equates to accuracy. Dr. Lou Palmisano imported a million pieces of virgin .220 Russian (aka 5.6 x 39 mm) brass as the parent case. The .22 PPC was born, load development and competition started in 1975 and the rest as that say, is history.

Many wildcats get adopted and standardized. A few examples are the 6.5mm-06 A-Square the above .22 PPC and its bigger brother the 6mm PPC; also the very popular .260 Remington

The Improved Cartridge[]

The same reasons for a designer to create a wildcat hold true for the improved cartridge. Just the name belies the reason. The person that is developing the cartridge wants to improve the existing commercial cartridge.

Now here is where things can get confusing. A purist would say an improved cartridge is not a wildcat because a wildcat cartridge cannot be chambered in any other chamber and safely be fired. However, a parent cartridge can be safely fired in an improved cartridge's chamber. Here are a few examples:

  • A Springfield .30-'06 cartridge can safely be fired in Improved .30-'06's chamber
  • A .300 H&H Mag can safely be fired in .300 Weatherby Magnum's chamber
  • A Winchester .30-30 cartridge can safely be fired in an improved .30-30's chamber
NOTE: Never discharge a rimless commercial cartridge in an “improved” chamber unless the headspace has been verified by a competent reloader or gunsmith.

The reason a purist doesn't believe improved cartridges are wildcats is the same reason that it is safe to fire a parent cartridge in an improved chamber. A parent case is a recognized, commercial cartridge. Typically the parent case has an unmovable head and therefore the headspace never moves. This would be when using rimmed or belted cases. The head on a rimmed case is the rim thickness. The head on a belted case s from the base of the brass or rim to top of the belt. Both rim and belt are fixed. Any part of the a cartridge case past the head has no effect on headspacing. Therefore, the parent case will chamber, headspace properly and fire safely. Again, the purist believes that since firing recognized, commercial ammunition or reloads in the chamber of the a barrel stamped “Improved”, the cartridge cannot be a wildcat.

The rimless case is a bit more complicated because the head is from the base of the cartridge to the middle of the shoulders or case mouth. Both those places can move. If the shoulders or case mouth is moved backwards in by the chamber reamer, you will have no headspace and the cartridge will not chamber. If the shoulders or case mouth is moved forwards by the chamber reamer, you will have excessive headspace; the cartridge will chamber and discharge. This will cause damage and or harm to both firearm and shooter alike. The trick is to design a chamber that will allow a commercial rimless cartridge to properly headspace in the improved chamber without changing the shoulder or case mouth headspacing measurement.

Commercial Terminology[]

To the commercial world any cartridge not manufactured by a commercial ammunition company is a wildcat (reloading that commercial ammunition exempted).

An example of the difference between the common thinker and corporate thinking is the 6.5 Creedmoor. As of November 2010 this cartridge has not been adopted or otherwise standardized by SAAMI or CIP. Therefore there are no standardized drawings for gunsmiths and reamer makers. More importantly, as this is a rimless case, there is no established headspace. To corporate thinking and commercial terminology, because the 6.5 Creedmoor is commercial available from Hornady Manufacturing it is not a wildcat.

However, to the common thinker and in provincial terminology, because the 6.5 Creedmoor has not been standardized it is a wildcat.