120MM XM866 TPFSDS-T Projectile

[apfsds]

Posting some photos of two US 120MM XM866 TPFSDS-T inert projectiles. To the best of my knowledge, this target practice round and its tactical counterpart, the XM827 APFSDS-T, were created for temporary use until the M865 TPCSDS-T and M829 APFSDS-T rounds finished undergoing R&D to be type classified. The XM866 and XM827 were not used very long.


Jason



A sectioned & non-sectioned example of the XM866 TPFSDS-T projectile.



LEFT TO RIGHT: Sectioned XM866, Non-Sectioned XM866 (appear to use an almost identical sabot used on the German DM38 / US M865), German DM38 TPCSDS-T, Ported Cone Stabilized early MOD M865 copied from the German DM38, Grooved Cone Stabilized M865, Current Grooved Cone Stabilized M865)

 

[Przezdzieblo]

Very interesting. Do you have an idea what was "maximum range limit" control mechanism on that? Fins looks normal, ballistic cap too. With no "governor" it could fly, fly and fly...

 

[apfsds]

I have often wondered how range reduction is established with this projectile, if at all? It does not appear to use the LKL Principle like fluted or ported cone stabilizers do. I could not find a lot of information about the XM866 TPFSDS and XM827 APFSDS-T projectiles other then that they were created solely as temporary ammunition when the US upgraded from the M1 Abrams tank using the M68 105MM rifled gun to the M1A1 Abrams fitted with the German M256 120MM smooth bore gun. These rounds were very quickly replaced with the M865 TPCSDS-T and the M829 APFSDS-T rounds as soon as they were type classified.

While I do not think this is the case with the M866, I am aware of some Israeli 105MM TPFSDS-T ammunition that is fitted with two small internal charges embedded halfway up the sub-projectile dart that after a known distance is designed to detonate causing the dart to break in half causing both pieces to fall to the ground with-in a safe distance

Jason

 

[US-Subs]

I don't know the answer to this projectile, but we were briefed (years ago) on experimental items that were tested with intentional inherent stability issues. Accurate out to a certain distance, then they would lose stability and begin to tumble. Just a thought....

 

[bdgreen]

Several examples of safety range limits engineered into TPFSDS tank ammunition from companies that produce such ammunition:

IMI’s 105 mm TPCSDS T M420 4, 2013
“The 105-mm TPCSDS-T M420/4 round employs a unique cone-stabilizer concept to reduce the safety zone required for tank gunnery, and it allows practice firing in short-range training areas."

IMI’s 120 mm TPCSDS T M324, 2013
“The M420/4 has a similar trajectory to that of the combat APFSDS-T round M426 (DM63) – up to a range of 2000 meters.” The TPCSDS-T M324 is the 120-mm kinetic energy Target Practice- Cone-Stabilized Discarding-Sabot Trace red cartridge for NATO 120-mm smooth-bore gun. The M324 training round utilizes a unique cone-stabilizer to limit the safety zone required for tank gunnery.”

ATK’s 120 mm M865 TPCSDS-T, 2012
“The M865 TPCSDS-T uses a unique, patented conical fin to provide a flat and accurate trajectory for target ranges. After passing the target range, the projectile velocity drops off sharply to limit the maximum range to 8 km. This safety feature allows for use on U.S. and European ranges where permissible projectile travel is limited.”

 

[Przezdzieblo]

It is possible then that XM866 range was not artificially limited...

As for TPFSDS`s range reduction mechanisms, there are few more, patented, but not introduced. I know Polish idea, with aditional disc-shaped brake in front of conventional fin stabilizer. In late 1970s there were at least two more interesting concepts, Canadian STUP (spinning tabular projectile), and US design with ablative nose. Range control was accomplished by, respectively, choking effect of air flowing through empty cylinder, and by melting of zinc tip, that was connecting three petals of ballistic cap. Second idea was finalized in US TPFSDS M797, training analog of M735.

 

[apfsds]

While I have no clue if the XM866 even incorporates a range reduction design feature as it is not apparent to me visually, I am aware of a few different methods concerning other tank fired TP ammunition. The most common range reduction design feature used on tank TP rounds is the use of a "Cone Stabilization Assembly". Instead of using fins to stabilize the sub-projectile in flight, this type of ammunition uses cone stabilizers with either precisely drilled holes or with fluted grooves manufactured in them to reduce overall distance. This aerodynamic principle is called the LKL Principle or, "Loch Kegell Leitwerk" effect. The holes and grooves in the cone assembly are aerodynamically "OPEN" at extreme speeds. Over distance when the sub-projectile slows, these holes or fluted grooves are aerodynamically "CLOSED" at an engineered known distance. This increases drag and the sub-projectile becomes unstable and falls to the ground with-in a safe range approved distance.



This photo shows various tank fired TPCSDS-T cone assemblies, fluted and ported.



This photo shows the internal charge used as a range reduction design in an Israeli 105MM TPFSDS sub-projectile.



One of my favorite range reduction designs is used on the US XM797. In this case the sub-projectile dart is pre-fragmented all the way down its body in two pieces. A fin assembly holds in together at its base and a specially designed windscreen made up of a soft metal holds it together at its top. When fired, the XM797's dart travels at a flat trajectory for a known distance. As aerodynamic heating increases over distance, the windscreen melts causing the dart to split in half resulting in the tail fins, windscreen and two body pieces all falling to the ground with-in range limits.



Photo of a non-sectioned XM866 TPFSDS-T projectile on the left of a sectioned XM827 tactical APFSDS-T round and a sectioned M866 TPFSD-T projectile on the right. Note the coke bottle shape of the dart. It is the same in the TP and tactical examples so not sure if this shape has anything to do with range reduction?

 

[mannra]

What are the darts Made of if anyone knows. I have one minus the fins and have considered making a hammer forged knife out of a portion of it. Worried about the dust particles and shavings though. I ran an Alpha/beta detector over it and it came up clean so not worried about DU.

 

[HAZORD]

I wouldn't expect the steel in those practice darts to be of any special quality that would make a decent knife that would hold an edge. Get a good piece of A2 tool steel, get it cherry red, and hammer it to the shape you want, heat it cherry red and let it cool in the air, then grind on the edge. A2 is air hardening tool steel. Excellent for knives.