Amron 40x53mm XM209

This is highly off my main interest. I decided to reward the seller for a very enthusiastic story about this experimental piece. Since I don’t know how the final insides look in a real 40mm production, may someone fill this void for me? The projectile is non matching for the cartridge and is placed here just to indicate what’s being discussed.

Vlad, is this a 46mm or a 53mm case?


Ok, and what is the model number indicated on the projectile?
And is a lot number given?

Alex, the projectile does not belong to it, the seller did not even want to give it to me, I took it anyway. He said that this cartridge’s gun powder well released too much pressure and to correct this, the final production model had a grid installed above this well to allow incremental release of pressure (or something like this, if I understood correctly). The projectile says “CTG 40mm practice M385”

Vlad, here the regular case design that is used today: … c-804s.jpg

The one you got might well be from some experiments of which there are quite a lot as the whole system was researched/tested a lot before it worked as required.

Alex, thanks. I can see it now. The dome is inverted in your picture (as compared to my round) so the pressure is released through a narrow point in your case.

Vlad, that is the so called “high-low” pressure system.
As your case is nor completely loaded it is possible that the cover of the propellant cavity we can see is just missing. As mentioned before there are many different designs and when looking at other manufacturers like German ones who are supplying the US also other systems are employed.
It may be very difficult to find a matching documentation on your case but maybe a formerly loaded and fired one may show up which could reveal the final configuration and appearance.

Vlad, this particular 40 mm case is designated XM209 and does not use a high/low pressure system. It was unique to the XM678 canister loading and used in the XM182 weapon system.

As usual, Fede nailed it.

From which book did you get the picture?

From which book did you get the picture?[/quote]

I can’t remember as this was scanned several years ago. I think it might be from the DOD test report on the XM678 cartridge.

I tried to include a photo of the XM182 but seem to have misplaced it in my albums. The XM182 was a pintle mounted, flexible 40mm grenade launcher mounted on an M113 APC for convoy duty in Vietnam. The basic gun is the M129 high velocity electrically driven launcher normally used on helicopters. The cartridge and gun package was developed to provide quick suppressive fire to counter jungle ambushes of truck convoys.

Ordnance, thanks a lot for the image!!!

I located the old posting from ordnance on the BOCN forum with the picture of the cutaway XM678 and XM182 gun system


The XM182 was also adapted to Cadillac Comando armored vehicles used by the Military Police, and Willys 4x4 (flexible mounting without turret).

FWIW: The Small Arms Review’s online document archive hosts a 1969-vintage document from Hughes Tools discussing the progress of their various arms projects. (S00173.pdf)

In the section on 40x53mm grenade launchers, there is a listing of current service and experimental ammunition types. The XM678 is listed as being under development by Nortronics. However, instead of the 54 tungsten pellets, the document gives the payload as only 32 0.24" carbide pellets.

As an aside, there is also mention of their 5.56mm Telescoped Caseless cartridge and their various Chiclet/Lockless developments, both polymer-cased and caseless.