Using all available public data I have re-created a 3D printable PGU-13 HEI and PGU-14 API 30x173mm round used in the mighty GAU 8/A Avenger autocannon on the Fairchild Republic A-10 Thunderbolt II.
This listing is for both the API and HEI rounds. I have optimized the design to make it easier to 3d print without supports and improvised where data was unavailable, so I cannot promise 100% accuracy. But it will print 1:1 scale with no issues. For the HEI PGU 13, I recommend utilizing a 6mm wooden dowel to align and pin the parts together (or you can 3d print pins as needed).