30 Herrett SLAP Load Development (Part 1?)

A cross-section of a 7.62×51mm SLAP cartridge

Saboted Light Armor Penetrator (SLAP) is a ammunition load designed to perform against light armor and softskinned vehicles. SLAP loads have been produced for both .50 BMG (M903) and the 7.62×51mm (M948) cartridges. Most recently, SLAP reentered public awareness when a gun YouTuber nearly lost his life when his Serbu RN-50 rifle explosively disassembled itself while testing M903 ammunition performance.

Scott DeShields Jr. suffered life threatening injuries

Of course, that doesn’t explain why I’m talking about SLAP, much less what .30 Herrett is or how it relates to SLAP. It all started a few weeks ago when I started watching an anime, Fate/Zero, on Netflix.

The main character wields a Calico M950A submachine pistol and a Thompson Center Contender hunting pistol as his weapons of choice. In reality, being a single shot break action pistol, the Contender is almost completely unsuitable for gunfighting. Either way I immediately thought it was cool and decided I needed one right that moment. (See my near autistic post about cloning the contender.)

The protagonist, Kiritsugu Emiya, examines the Thompson Center Contender in episode 3.

An afternoon of browsing Gunbroker later, I found myself the proud new owner of a first generation TC Contender with a 10″ barrel chambered in .30 Herrett.

.30 Herrett is a really interesting cartridge. It’s a wildcat cartridge using a reformed and shortened .30-30 Winchester case. Specificlally designed for use in the Contender, it was developed by Steve Herrett and Bob Milek in 1972. The Western Powders blog and Hornady are both excellent sources of information on the cartridge.

At some point, I think the plan was to replace the barrel with one chambered in .223 Remington, but while looking around for information on the cartridge, I found this post on 4chan’s /k/ board.

A thoroughly bad idea, right?

You see, reading this post started a train of thought that ended somewhere around 6 fingers of Hibiki Suntory whiskey and an evening voice chat in a Discord call with a few others. At some point, we figured out that you could order “tungsten scribe tips” from various Chinese manufactures. Why a “scribe tip” would need a boat tail is beyond me, but it sure looks an awful lot like a tungsten bullet doesn’t it? And since the .30 Herrett uses a .308 caliber projectile, the .308 sabots are a perfect fit. I’m sure you can see where this is going.

A insane idea takes form

The big, big, big disclaimer here is that as awesome of an idea as this sounds, actually manufacturing this ammunition would be illegal.

(a) It shall be unlawful—
(7) for any person to manufacture or import armor piercing ammunition, unless—
(A) the manufacture of such ammunition is for the use of the United States, any department or agency of the United States, any State, or any department, agency, or political subdivision of a State;
(B) the manufacture of such ammunition is for the purpose of exportation; or
(C) the manufacture or importation of such ammunition is for the purpose of testing or experimentation and has been authorized by the Attorney General;

18 U.S. Code § 922 (Link)

18 U.S. Code § 921 goes on to define armor piercing ammunition:

(17)
(B) The term “armor piercing ammunition” means—
(i) a projectile or projectile core which may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium; or
(ii) a full jacketed projectile larger than .22 caliber designed and intended for use in a handgun and whose jacket has a weight of more than 25 percent of the total weight of the projectile.

18 U.S. Code § 921 (Link)

To actually manufacture this, from what I understand, I’d have to either have my own Class 10 FFL, or make this ammunition under a Class 10 FFL. Considering that this is a cartridge designed for a pistol, there seems to be additional legal issues for making specifically armor piercing handgun ammunition. (Ignoring how a break action, single shot pistol isn’t a seriously plausible combat sidearm in the 21st century.)

After playing about in a cartridge load calculator, trying to determine the density of tungsten for a given projectile size and antagonizing Atlas Arms over the Dagney Dagger on Twitter and looking at existing load data, the idea of .30 Herrett SLAP took firm hold of my brain and I decided to leap headfirst down the handloading rabbithole to see if this ridiculous meme was anywhere near realistic.

According to load data from E. Arthur Brown Co., using a 55gr saboted projectile throught a 14″ barrel, velocities of 3,300fps are theoretically possible. It’s very likely that these calculations do not account for the weight of the sabot itself. (Approximately 7gr per sabot.) Tungsten is obviously more dense than copper jacketed lead or steel, and would be heavier by size than a comparable projectile.

Cursory projectile weight estimations

Ignoring the reduction in mass from the point, and estimating a projectile generally the same length as a common 55gr .224 caliber bullets, a weight of around 119gr would result. This is obviously a lot heavier than the 55gr projectile that was used as the basis of the sabot load data, and would move significantly slower than the estimated 3,300fps. At those weights and velocities, it’s doubtful the projectile would be armor piercing. But I can play with QuickLoad all I want and see what’s theoretically doable.

The next steps for load development are as follows:

  • Determine tungsten projectile shape
  • Calculate tungsten projectile weight
  • Find a Class 10 FFL to handload this insane cartridge
  • Consult a lawyer about the legality of manufacturing this cartridge

Another post will follow if more progress is ever made.

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