Piston Launching Projectile XM5

I picked this up recently.

I can find information about it, but can’t quite visualize how it works.

The markings on it are as follows:
FSN 1195-897-5171
PN 8845109
DATE - 4-62

The case is not magnetic, I thought I read that it is titanium.

This case separates from the projectile down range, 150 to 350 meters.

Any insight is appreciated.



Great item! Thanks for posting. It was used with the Davy Crockett weapons system.



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More pictures:

Looking from the bottom at the strainer.

From the top looking down the length at the strainer.

A view of the bayonet lugs and index tabs.

Indeed a nice find. Not spectacular in appearance but technical and historical context is unbeatable.




The use of titanium was required to meet the weight limit specifications of the weapon. The development of the alloy was sponsored by the Watertown Arsenal Laboratories and the piston was also manufactured at this arsenal (WA). According to US documentation, it was the first US Army gun made of titanium.

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Fede, the Titanium used there was not from the USSR by chance?

Much like the titanium drag stabilizers used with some bombs, these things were very expensive to produce / procure, and it always amazes me at the low resale prices these things sell for today, if at all - many are dragged out of water or picked up for free.

Alex, I’m only speculating, but there is a strong chance that the titanium was supplied by TIMET (Titanium Metals Corporation of America) in Nevada. They started producing titanium in the early 1950s and according to their website they produced the world’s first titanium ingot in 1952: http://www.timet.com/about/timeline-of-milestones.html

Fede, do you know which titanium alloy was used for the piston? The metallurgist in me would love to know.


Very interesting item! Thank you for sharing the photos here.

That seems to be for the 120mm gun. Is that about what the outside diameter is?

Regarding function, I’m guessing the strainer allows some pressure from the launch charge into the interior of the piston and, as inertial forces pinning the piston against the super-caliber projectile’s base dissipate, the pressure cleanly separates the two with the projectile’s engaging lugs riding out the angled bayonet slots in the piston wall.

Does this sound right?


Alex, I don’t know who was their source, but the US already had large scale manufacturing operations since the late 1940’s.

@LarryF264 Larry, they used Grade 6Al 6V 2Sn titanium alloy.



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The O.D. of the case is about 118.65mm. The O.D. of the obturator ring is about 121.83mm

Very VERY cool!