US 90mm L/88 Hypervelocity Gun Project "A-Z" (1945-46)

[RyanC]

The ultimate goal of NDRC's Division 1 (Ballistics) was to design Project A-Z, so named because all phases of the Division's program (from A to Z) would be used during it.

It was to be a 90mm gun with a chromed bore/chamber (this did not appear on production tanks until I think the M1A1s M256 gun).

Furthermore, it would fire pre-engraved projectiles and have the following specifications:

90mm L88
23.8 lb projectile @ 4,200 FPS
60,000 PSI chamber pressure
760 in3 chamber

The end of the war halted development of A-Z, although six barrel forging blanks had been cast by then. During machining of the heat treated forgings, cracks in four of them were found and they were rejected. The remaining two tubes were machined (exterior wise) and sent to Watervliet Arsenal in April 1946 as smoothbores, ready for rifling; the Ordnance department had agreed to complete them and test them, while the Naval Gun Factory had agreed to chrome plate them with the help of the National Bureau of Standards.

 

[GARGEAN]

So were they tested in the end?

 

[Apophenia]

It would seem not. Division 1 was investigating both sabotted 90 mm rounds and pre-engraved projectiles (akin to their .50-cal PE rounds).

https://archive.org/stream/hypervelocitygun01bush/hypervelocitygun01bush_djvu.txt

"Preliminary tests of the final design of an all-steel 90-mm sabot-projectile with an 8-lb tungsten carbide core, which were made just before the work was terminated, indicated that by the use of such a projectile the muzzle velocity of the standard gun was raised from 2,700 to 3,700 fps. The projectile’s accuracy was as good as that of the standard 90-mm projectile. [...]

EXPERIMENTAL HYPERVELOCITY GUN

After Division l’s investigations had yielded a rational explanation of the phenomenon of gun erosion and had pointed the way toward the development of erosion resistant materials, an attempt was made to apply this new knowledge to the development of a practical hypervelocity gun. The first step in this direction was to have been an experimental 90-mm gun firing at a muzzle velocity of at least 4,000 fps. Two tubes for this gun, chambered and bored but not rifled, were prepared before the termination of the Division’s activities and then were turned over to the Army Ordnance Department for further development. According to the original plans these tubes were to have been chromium plated and were to have fired pre-engraved projectiles, and thus make use of the experience gained in the trial of the 37-mm tubes."

 

[RipSteakface]

Very very interesting. I wonder if it could have been fitted into an appropriate tank like a T32.