Hello fellow Hornet Drivers,
Just a little background on me, I do ballistics work for the ArmA III community on projects like NIArms/HLC, SMA, RHS, EricJ, and I even contributed to the ACE III team. I have also been a ballistics developer and military hardware consultant for other games like Occupation Source and the Modern Warfare mod for World In Conflict, and am being considered for a paid developer position doing ballistics for Ground Branch, details still being worked out on that position currently.
As for my suggestion, it has come to my attention that while the Hornet is still in Early Access (like so many of the modules in DCS) and stuff like ammunition for the gun is WIP, I saw that the F-16C had quite a selection of 20mm ammunition and the Hornet just gets Default and No Tracer, this got me interested in finding out if the USAF, USN, and USMC use different ammunition, in fact they DON'T both use the same DODIC ammunition from 2 suppliers Orbital ATK (Now completely merged with Northrop Grumman) and General Dynamics. It is confirmed that the F/A-18C uses both the M50 and PGU series of munitions, I can not attest to the F-16C as my research was entirely focused on the F/A-18C, but both services do use the same DODIC ordering information that much is confirmed.
Here is a list of ammunition that a F/A-18C Lot 20 would use:
M50 Series:
M55A2 Target Practice (TP)
M220 Target Practice Tracer (TP-T)
M56A4 High Explosive Incendiary (HEI)
M242 High Explosive Incendiary Tracer (HEI-T)
PGU Series:
PGU-27 A/B Target Practice (TP)
PGU-30 A/B Target Practice Tracer (TP-T)
PGU-28 A/B Semi-Armor Piercing High Explosive Incendiary (SAPHEI)
Here I will provide detailed information with links included to back up my claims, despite what people might think (and have told me in the past) this information is NOT CLASSIFIED, it is publicly sourced and all information is official.
F/A-18C Hornet M61A2 Lightweight Vulcan Official Information from General Dynamics: https://www.gd-ots.com/wp-content/uploads/2017/11/F-A-18-C-D.pdf
General Overview of the rounds via NavyBMR (training program): http://navybmr.com/study%20material/14313a/14313A_ch7.pdf
M55A2 & M220 Official Information via Northrop Grumman: https://www.northropgrumman.com/Capabilities/MedCalAmmunition/Documents/20mmM55A2TPFactSheet.pdf
M56A4 HEI (M56 Series) Official Information via Northrop Grumman: https://www.northropgrumman.com/Capabilities/MedCalAmmunition/Documents/20mmM56HEIFactSheet.pdf
M242 HEI-T Orbital ATK (defunct) Official Information: http://212.178.67.161/ftp/20mmcollector/20mm/HEI/20_102_M242_HEIT_ATD.pdf
PGU-27 A/B TP Official Information via General Dynamics: https://www.gd-ots.com/wp-content/uploads/2017/11/20mm-PGU-27-A-B-F-15.pdf
PGU-30 A/B TP-T Official Information via General Dynamics: https://www.gd-ots.com/wp-content/uploads/2017/11/20mm-PGU-30-A-B-F-18.pdf
PGU-28 A/B SAPHEI Official Information via General Dynamics: https://www.gd-ots.com/wp-content/uploads/2017/11/20mm-PGU-28-A-B-F-16.pdf
In all honestly the only 3 rounds we would "need" would be the M56A4 HEI, M242 HEI-T, and the PGU-28A/B SAPHEI, but I included the training rounds to fill out the list based on authenticity. I hope that "Wags" or other developers for the DCS F/A-18C module see this post and are able to use the information within to polish off the ammunition selection, each of these rounds impacts targets differently, and we are currently able to switch from M50 to PGU ammunition in the Hornet so that functionality is already there, this just completes that "subsystem".