View Full Version : What cartridge is this?

December 5, 2009, 11:10 PM
Backstory: At my office we have a division devoted to guns. One of the graybeards (since retired) had an inert cartridge sitting on his desk. I'd never seen anything like it before so I asked him about it. He said that the cartridge had been in his desk when he got it and that's all he knew about it. I asked him if he minded if I took a picture of it because I really wanted to know what it was. He didn't mind. I took the picture....

...That was probably 10 years ago. I still have no idea *** the round is. Nobody I've ever talked to has any idea. What I recall from my efforts...

Bullet is 5.56 mm.
Case is too long to be 5.56 NATO. Besides, the shoulder isn't pronounced enough.
Obviously, it was intended to be belt fed...with a PLASTIC belt!

Anybody have a clue?

December 6, 2009, 12:37 AM
Kind of an obvious question: what does the head stamp say?

December 6, 2009, 12:38 AM
There was no head stamp.

edit: I should say that I'm pretty damned confident that this was an experiment by the military. Obviously a failed experiment (or at least one that didn't make it to production). I'm just curious if anybody recognizes it.

December 6, 2009, 01:05 AM
I would tend to agree that it is an experimental military cartridge. The reasons for my thinking this are:
* Apparently smaller diameter than a 5.56X45, judging by the minimal shoulder.
* Longer than a 5.56X45 by about 1/2", almost as long as a 7.62X51mm NATO round.
* Belted case (uncommon in cartridges other than magnums).
* Plastic link belt (links are pretty much a military thing, since they are used for feeding automatic weapons).

December 6, 2009, 07:48 AM
This is a real oddball, and probably worth its weight in (well, probably not gold, but some other precious metal) to a collector that specializes in this sort of unusual dead-end in military cartridge development. I think that this is a version of the XM645 5.6x57mm SPIW (Special Purpose Individual Weapon) round, in a disintegrating link for the LMG version of the weapon; the case is distinctive enough that it narrows it down to one of the SPIW cartridges, but the really odd thing is that it should be loaded with a discarding-sabot "puller" flechette; has this round maybe been fired, and the bullet replaced with a pulled M193 ball bullet? You may be able to get some more definitive info on it at http://iaaforum.org/forum3/index.php

XM645 cartridge, next to the earlier XM144 and XM216 cartridges:


Whole and sectioned XM645 cartridge, at the far left:


Photograph of one of the "Universal Machine Guns" designed for the SPIW cartridge:


284 Win
December 6, 2009, 08:03 AM
It sure looks a 375 H & H magnum to me but the belt looks a bit wider, hard to tell from a photo, a person would have to measure the dimensions, to be able to tell exactly what it is.

284 Win

Jim Watson
December 6, 2009, 10:10 AM
Agree with SDC. I had gone back as far as Project Salvo and was seeing similar stuff, but the skinny belted case is distinctive.
Maybe some dinosaur who didn't trust the fletchettes that were the fad of the era got some loaded with real bullets. Well, it looks like a bullet, only smaller.

December 6, 2009, 10:49 AM

Thanks! As for the mystery of bullet vs. flechet round? I have no idea. As for whether or not it had been fired? I no longer remember and I no longer have access to the cartridge (the owner retired and took it with him). Still, thank you very much. As I said, this one has been bugging me for a decade.

December 6, 2009, 05:53 PM
SDC, what is the turned hollow base bullet at lower left? It llooks like a screw machine product for a .45 ACP, but the reversed ogive shape must have a purpose. Judging by what I see it also looks very light, high velocity, maybe the shape is designed to do something special to the target? Fascinating projectile.

B. Lahey
December 6, 2009, 06:14 PM
what is the turned hollow base bullet at lower left?

Looks like a .45 THV AP round.


December 6, 2009, 07:26 PM
Exactly, it's a THV ("tres haute vitesse"/"very high velocity") made by SFM of France, but also produced in South Africa and a couple of other countries. These use a combination of light weight, hardness (they're machined bronze), and very high speed to pierce Kevlar, by concentrating all the force on a very small point at the tip of the bullet, the same way that an arrow works. The 9mm to the right and the 38 Special in the top row are by the same company.

December 10, 2009, 11:21 PM
I wonder what kinds of velocity they got with that. Also, as projectile weight goes down and velocity increases slide cycling becomes less predictable. My pastor loads some very high velocity necked down Tokarov cases, .22 I think. He says the spread between reliable cycling and kaboom is very small. :eek:

December 11, 2009, 10:32 AM
Factory specs on the 45 Auto THV say over 2000 fps, but don't mention what the barrel length was (5"?).

James K
December 12, 2009, 01:14 PM
SDC appears to be correct. I have two empty cases, one that appears to be the XM645, and the other to be the XM 144. All I know is they came from Aberdeen Proving Ground in the 1970s. The belted case is 57mm long, with a head diameter of .309, .294 ahead of the belt. The headstamp is IVI 71. There is no primer, but the pocket measures .173"

The other has no belt; it is 1.73" long and the head is .308. The headstamp is WCC 63. It has a primer, and best I can tell, it is smaller, about .160".

Contrary to the usual belief, a belt on a cartridge is not for adding strength to the head, but to assure proper headspace when there is no rim and not enough shoulder to do so. The XM645 (if that is what it is) has only a tiny shoulder and could never have had adequate case support without the belt.