Unusual 7.62x51 Duplex - follow-up to earlier posting


#1

Recently Gyrojet posted a picture of an unusual 7.62x51mm duplex -see below

I’ve made a few enquiries about this and according to the Woodin Lab (thanks for their help), the sectioned cartridge above is an exact match to a French 7.5mm duplex in their collection. Who, where and when this was loaded is unclear. There is apparently no record of Frankford Arsenal doing this. Gyrojet - please can you confirm that the headstamp is simply FA. Does the bullet have a colored tip?

Can anyone provide more information on the French 7.5mm duplex cartridge?

NATO Dave


#2

How does a duplex work? Surely on firing the second bullet would just jam up into the first and the two fly togeather? What causes them to seperate?


#3

Once I found such “two” bullets in Vietnam (Dong Ha / Cam Lo near Khe Sanh) - I assuemd them to be US since nothing else would make sense there. They were separated from the case but were somehow “connected” to each other. I do not know if they were soldered or held together otherwise. At that time I thought the connection between them is ripped when the front projectile is entering the rifling and starts rotating while the scond one is not and sowith the joint gets twisted apart.

Can anybody confirm or correct this?


#4

As I understand it, the thought was the bottom (or back) bullet had a canted base to supposedly veer it off the exact same course. (which is depicted in the expertly positioned bottom bullet sectioning by Paul Smith) I also understand that the theory was ok, but the practice was not.

There are a couple other multi balls in this file photo I have of this drawer…sorry the x-ray is obscuring some of the rounds.

The 7.62 RICA squeeze bore is a nice round (top row “center”)


#5

Vince

Both bullets are solid steel, copper plated, so they should not jam together in flight. (They occasionally did, despite the theory.) Additionally, the rear bullet had an angled base and reached a velocity about 500 fps slower than the first. So, in practice, the bullets did seperate.

The theory was that the two bullets would create a random pattern on the target increasing the hit probablility despite aiming errors. However, they did not cooperate. The first bullet struck where it was aimed but the second consistently struck in the same general area, only lower, depending on which weapon it was fired from.

The M198 was eventually discontinued. It’s first cousin rose again as the XM256 Low Recoil, but it too was abandonded.

They (Army, APG, WRA, whoever) did try different bullet combinations. I have one undocumented example that has different weight bullets and the rear one does not have an angled base. It may be that the one Gyrojet posted is also a legitimate alternative prototype.

Ray


#6

Here the picture of french 7,5x54 duplex and triplex of my collection.

This experiments have been conducted between 1968 and 1971.
Tomorow (it is late in France) I will seek more information on the projectiles.

Edit :
The projectiles have an aluminum core, a lead base and a soft steel jacket.
The two projectiles (glued) are 42mm long and they weigh 12 grams.

Here are all the information that I have.

Michel