Fascinating Experimental 105mm XM797 TPFSDS-T Projectile Design

[apfsds]

Of all of tank fired DS rounds I have in my collection, I find the design of the 105mm XM797 to be one of the most unique. I decided to deconstruct this projectile to study it better and to eventually make a full up sectioned inert round. Designed as a target practice round it was necessary to limit its over all travel distance so it could be contained on most firing ranges. Unlike most other tank fired target practice rounds that were typically designed with cone stabilizers to limit overall travel distance, the XM797 went a wildly different way. It incorporated a specialized windshield, I think made out of a zinc alloy, that is designed to purposely fail at a certain known distance due to aerodynamic heating. When this happens, the dart body splits in half down its longitudinal axis along a pre-fragmented center line. I do not believe that the XM797 was ever adopted and I have never seen any of its design features incorporated into other projectiles.

Jason

 

[SG500]

Nice job Jason, you did well taking that one to pieces so well.
Thanks for showing it. I never even knew one like this existed.
Dave.

 

[apfsds]

Thanks big time, Dave! I will be on the hunt for one for you.

Jason

 

[Przezdzieblo]

... and patent on it --> click

 

[apfsds]

Thank you so much for the link to the actual patent on this projectile! I printed it out for my files and just read it. It was cool to learn the inventor's name and that the patent shown is a slightly early design as my projectile has some very minor differences. I have seen a few XM797 specimens and they all were split into 2 equal segments down the length of the sub-projectile dart. The patent shows it cut into 3 segments joined at 120 degrees to each other. The patent also shows a different way of attaching the fin assembly to the darts body. I like how the inventor put in special verbiage disclosing how he may make subtle changes in future designs that he wants protected under the original patent. Very cool to see the history of its creation out of someones mind. Greatly appreciate the info!

Jason

 

[apfsds]

I just heard back from a friend of mine who works for one of the big ammunition manufacturing companies who confirmed that the XM797 TPFSDS-T round was never adopted for service. He also told me that it was designed and called a "Self Destructing" TPFSDS-T round. This is also mentioned in the patent link. That is was designed to self destruct at a known distance as a way to limit overall travel distance vs a LKL cone stabilized assembly that is designed to become aerodynamically unstable as the sub-projectile slows down with distance causing it to tumble and fall to the ground. The only other "Self Destructing" TPFSDS-T tank round that I am aware of is an Israeli 105mm that has 2 small explosive charges embedded inside the sub-projectile's dart body that blows the tail assembly off mid flight at a known distance. I think those 2 charges are initiated by the tracer?

Jason

 

[Przezdzieblo]

Jason,
something for you, 1977 stuff:



Adding an ablative nose in means of range control was also proposed for 105 mm TPDS-T M724.

 

[apfsds]

Thank you again for your help. GREAT diagrams! I just saved both of the photos. I like how these show the sub-projectile pre-fragmented in 4 sections.

Jason