Using all available public data I have re-created a 3D printable PGU-14 30x173mm API round used in the mighty GAU 8/A Avenger autocannon on the Fairchild Republic A-10 Thunderbolt II.

I have optimized the design to make it easier to 3d print without supports and improvised where data was not available, so I cannot promise 100% accuracy. But it will print 1:1 scale with no issues.