I've been workshoping a system for physicaly determined damage. Many guns would require changes to available ammo, recoil, and handling, but I like the numbers it puts out. The durable damage is low for the modern game but alligns pretty well with the release version; That could be updated.
Damage is proportional to Velocity Squared and Cross Sectional Area. Durable damage is proportional to Velocity and CSA. The system doesn't give good results for low velocity rounds(could be fixed for pistol rounds by upping Velocity to realistic levels).
Key: *changed*, 'added'
AP2:
Carbine(*870mps*): 70(8)
Liberator(5.5mm 900mps): 75(8)
Tenderizer('6.5mm'): 85(10)
'Justice(7mm, 910 mps): 125(14)'
AP3:
Penetrator('.66xdamage'): 60(6)
Adjudicator(8mm 820 mps): 130(16)
Verdict(*450mps* '1.5xdamage'): 135(30)
Ammendment('8mm'): 140(17)
Diligence(9mm 850mps): 220(26)
Senator('1.5xdamage'): 235(43)
Dill CS: 270(28)
Deadeye(*more drag* '9.5mm, 1.5xdamage'): 300(35)
'Camper(10mm 1000mps): 305(31)'
AP4:
HMG(*800mps*): 305(38)
HMG Emp(12.5mm 880mps): 370(42)
AMR('baked-in 80 explosion'): 450(122)
Notes: mg43 same as Adjudicator, Constitution same as ammendment, stalwart same as carbine.
Edit: I accidentally calculated the Diligence and DCS at 10mm. They should be 180(21) and 220(23) respectively.