I was making these pics for someone for a potential trade and decided to post them on the Forum for the “Big” guys.
In 1981 the AF awarded a contract to AAI in MD to produce an APDS round for the A-10 with significantly increased effectiveness compared to the DU round currently in service. The round was designed around flechettes (in both Tungsten alloy and DU I understand). There were a number of variations produced for testing, and the ones I have seen all have a fleschette that almost reaches the bottom of the case and white plastic (nylon??) sabots. The cases were all the OD color aluminum pictured below. I think the testing went on into the mid 1980.
The initial trials showed that an APDS round offered significantly increased kill probability. A question arose on how well these rounds would feed through the drum and tray system on the A-10. To study this, AAI delivered to the AF in Aug 1983, 36 of the dummies pictured below. They were packed in vertical paper tubes in a 20mm ammo can.A copy of the label is pictured below. The projectile is a mockup of the actual with an aluminum body with a steel tip above the driving band. I believe the steel tip extends down the core of the aluminum body. When I look in the primar hold, it looks like the steel core goes most of the way back to the base of the case. This would make sense since the dummy would need the same center of gravity and mass distribution as a loaded round. I have seen cutaways of the loaded version of this cartridge with the same ogive, and they have the two black plastic driving bands that are on this projectile. Most of these were damaged during the testing which led ot a re-profile of the projectile to cover more of the tip and taper more toward the front. I believe this particular projectile shape was dropped by the end of 1983 or early 1984.
The ogive change seems to have solved the feed problem, but I have never seen a dummy with the new ogive.
The problem tha caused the project to be cancelled was much more complicated. The A-10 has two rear mounted engines. The concern was that some of the hail of plastic sabot sections from the firing of these cartridges would be sucked into the engines and damage them or cause them to flame-out during the firing run-bad news in combat, or even in practice. The solution was to mount a sabot shredder in front of the gun. It was about the size of a small garbage can with a number of counter rotating blades. Down the middle, inside the axis on which the blades rotated was a tube down which the flechette would travel after the sabot seperated into the shredder blades. The muzzle blast would spin the blades very fast, like the compressor on a jet engine. The sabots would be shredded into fine bits which wouldn’t damage the engines. The theory was fine, but reality intervened. When a long thin body like the flechette is accelerated very fast down a gun barrel it begins to oscillate and bend with an S-curve related to it’s resonate frequency. Once out of the gun barrel the flechette stops oscillating very rapidly, but in the configuration being tested on the A-10, there were only inches, or a bit more space between the end of the barrel and the sabot shredder. Most of the flechettes went down the tube in the shredder just fine, but occassionally one would contact the shredder with some force and when that happened, it blew the shredder off the front of the aircraft!!! Attempts to better support the flechette by extending the sabot further back into the case didn’t solve the problem and the program was terminated. I have seen cutaways of some of the later sabot designs and they are long and conical going back to the fins in some cases. They also had some complicated shapes. I suspect there may have been a problem with these later sabots taking up too much of the powder capacity of the case.