Sunday, March 20, 2016

Magic Bullet - The ARX

There are few pookas worth chasing (excluding Harvey the invisible rabbit) as much as the magic bullet.  The magic bullet has quite a few qualifiers, all or any of which make the chase worthwhile.

A magic bullet should (minimal list):
  • Feed in all guns under any conditions,
  • Know when to penetrate deeply and when to stop short,
  • Hold its shape and punch through sheet metal, wood and layers of cloth and leather but expand at least 4 times its diameter in flesh,
  • Fragment into dust when it hits a hard surface and not ricochet but retain its mass in tissue,
  • It should be legal in all states, especially in the Republic of New Jersey where each hollow point round carries its own draconic penalty,
  • It should be remarkable accurate and reproducible at varying distances independent of caliber.

That’s a tough list.

Top view of the ruger ARX bullet
Looking down on ARX bullet, it does suggest a three-bladed propeller. 

PolyCase and Ruger are entering the chase.  The bullet, called ARX by PolyCase Ammunition, “uses fluid dynamics instead of expansion to achieve superior terminal performance.” 

The secret, if it is a secret, is mathematically there isn’t any difference between an object moving through material or material moving around an object.  This is the principle used in testing a car or soapbox racer in a wind tunnel.

The almost propeller-like cross section of the bullet deflects media upward away from the bullet creating, in theory, turbulence.  In gelatin the turbulence creates separation.  In tissue this turbulence is equated to tissue damage.  Tissue damage is equated to stopping power.

These assumptions may not be true.  Tissue has grain and directionality giving it different physical properties in different directions.  The physical properties of gelatin are equal in all directions.  The damage caused in tissue may be quite different than what we witness in gelatin.

It is a truism from both the jello junkies and the morgue ghoulies a significant penetration of a bullet into the body is required to stop lethal aggression.

holding Ruger ARX polycase cartridge
Ruger ARX PolyCase round in 9mm

The two groups differ in how much penetration is required.  Both sides realize that a round that leaves the body carries off energy which would be better spent on destroying tissue.  

Getting that bullet to stop just under the skin on the opposite side of a 350 pound stoned biker and a 110 pound meth head is the problem and some compromise must be found.  That’s why there are so many varieties of ammunition available.
380 penetration image   

.380 in gelatin
I was unable to find a good image of a 9mm in gelatin so I'm making due with .380acp

Let’s look at this bullet.

I crudely ashed a portion of one bullet and found it was chiefly metal particles.  A smaller un-ashed sample was place in a Scanning Electron Microscope with an Energy Dispersion Spectrometer (it’s just a way of finding out what elements are present, nothing to be scared of here folks, just keep on reading) and I found out what the metals are.

You might guess copper (Cu) and you would be right.  There’s a second metal present, tungsten (W).  Tungsten is very dense so small particles are relatively heavy.  I don’t know anyone who makes a tungsten-copper alloy, but using two different metals is smart.  By varying the ratio of the metals you could get different weight bullets.

Elemental spectrum of  bullet

Backscatter electron image: the whiter the spots the heavier the element

the location of copper in Backscatter Image

the location of tungsten in Backscatter Image

The bottom of the bullet shows a small tit from a sprue gate.  That’s the point where the polymer is forced into the mold.  Most of the advertising photos don’t show this, but even located on the axis of rotation, this imperfection will add a tiny amount of inaccuracy to the bullet.  I don’t think it would matter to anyone other than the top marksmen.

Sprue gate mark from mold injection in bottom of bullet

I didn’t run solvent tests or do any organic analysis to determine what the polymer is present.  Safe to say it doesn’t melt, based on my ashing.

I picked up a box of 9mm and here’s that stats;
  • 9mm Luger +p,
  • 80gr bullet,
  • Muzzle velocity: 1445ft/sec,
  • Energy: 371 ft lbs.

Does it feed?  I test fired in two guns, a Glock 17 and my Kahr P9.  Both fed fine from a closed slide and a slide stop reload.  I test fired at a phone book 1.5 inches thick and the round just kept going.  I wasn’t surprised it wasn’t stopped, but I had a fantasy I would find the round in the ground behind it.  Trying to find a brown bullet on brown mud is an exercise for someone with more patience than me.

Where does this leave this contender for the title of Magic Bullet?

I didn’t fire enough rounds to determine if the round would leave residue in the barrel causing a blockage.  Not being able to recover the bullet meant I could not determine if the polymer was deformed.  Shooting through a phone book has no translation to stopping power. 

Of more interest to me is did the bullet pick up the tool marks present in the lands and grooves?  If the bullet can’t be matched to the barrel that fired it, an important piece of criminal evidence would be irretrievably lost.  I would suspect the government would ban such rounds, and in any case, I also suspect New Jersey would ban it, assuming they haven’t already banned composite bullets.

Another problem, from my perspective, is we really don’t know what the stopping power is.  What if it’s worse than FMJ?  What if it really does fail to penetrate deep enough in living, breathing hard-to-stop-people?  Or it could be like a .22LR, where people die two days later in the hospital and not DRT*.  I also don’t know if it will drop people like a phaser set on heavy stun.

There are similarly designed all copper rounds on the market.  But we still have the problem every magic bullet, in fact every self-defense bullet, must answer.  Does it provide stopping power equal to or greater than the same load and caliber with a FMJ round?

By now many of you know my philosophy.  Don’t be the poster child for stupid.  Let someone else determine its usefulness on the battlefield of self-defense and resulting legal entanglements.  If it proves to be a world beater, it will be around.  If not, then it’s a just a cool round to have in your bullet collection.

*Dead Right There

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