5.56mm duplex phase III Colt test rounds

What’s the meaning of “fluoroscoped”?


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With a duplex round these were X-rayed / fluoroscoped to see the position of the inner bullet before firing to be sure it was in the correct place after loading.

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Do cutaways exist?

I think I might have one, but not handy at the moment, Most of the variations did not have tip color & I believe red was also used.

There should be searchable threads on ACR trial variants

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Pepper, thanks a lot for the great overview!

An old picture I had, probably from Teak C.223ColtDupx1 Teak

Kudos for Paul Smith sectioning

I knew I had pictures somewhere!


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Paul, thanks a lot!
As you have handled the single projectiles, do you know how they are attached to each other? By solder?

No adhesive. Pressure fit and can come loose and appear on X-ray amongst the gun powder Certainly in 30-06 SALVO rounds

Here is a great image Pete posted in 2016.
IAA image
I wonder what percent did not separate when fired!

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Pepper, thanks a lot! I just wondered as I once in Vietnam found 2 still attached (7.62mm) but outside the case and they were attached to each other quite well.

I need an explination as to what these 2 rounds were developed for??
I know they are 5,56 or 223 but what do the bullets represent???

The red-tipped is the M196 Tracer made by Twin Cities. The lower round is a West German ‘Kurzbahn’. This is a short range training round.

Thanks Jim!!

The short range is a DAG development and I never saw one with a silver color plating.
Thank you for sharing!