Zygote,
IIRC, the damage looks like this:
If the Hispano MkII damage is 100, then the Type 99 MkII would be about 85. That is really close.
Tony Williams has the following listed for AH guns in his book "Rapid Fire":
NS-37
Projectile Diameter: 37mm
Projectile Type: AP
Projectile Weight gm: 735
Muzzle Velocity: 900 m/sec
Joules at the Muzzle: 298,000
Used in AH By: Yak-9T
FlaK 18
Projectile Diameter: 37mm
Projectile Type: HE
Projectile Weight gm: 640
Muzzle Velocity: 820 m/sec
Joules at the Muzzle: 215,000
Used in AH By: Ostwind
MK 108
Projectile Diameter: 30mm
Projectile Type: HE
Projectile Weight gm: 330
Muzzle Velocity: 505 m/sec
Joules at the Muzzle: 42,100
Used in AH By: Bf109G-6, Bf109G-10, Fw190A-8, Me262A-1, Ta152H-1
VYa
Projectile Diameter: 23mm
Projectile Type: API
Projectile Weight gm: 200
Muzzle Velocity: 880 m/sec
Joules at the Muzzle: 77,400
Used in AH By: Il-2 Type 3
Hispano MkII / M2
Projectile Diameter: 20mm
Projectile Type: HE
Projectile Weight gm: 130
Muzzle Velocity: 880 m/sec
Joules at the Muzzle: 50,300
Used in AH By: F4U-1C, Hurricane MkIIc, Mosquito FB.MkVI, P-38L, Seafire MkIIc, Spitfire MkVb, Spitfire MkIX, Typhoon MkIb
ShVAK / B-20
Projectile Diameter: 20mm
Projectile Type: HE
Projectile Weight gm: 97
Muzzle Velocity: 860 m/sec
Joules at the Muzzle: 35,900
Used in AH By: La-5FN, La-7, Yak-9U
Hispano MkV
Projectile Diameter: 20mm
Projectile Type: HE
Projectile Weight gm: 130
Muzzle Velocity: 850 m/sec
Joules at the Muzzle: 46,900
Used in AH By: Tempest MkV
Type 99 MkII
Projectile Diameter: 20mm
Projectile Type: HE
Projectile Weight gm: 128
Muzzle Velocity: 750 m/sec
Joules at the Muzzle: 36,000
Used in AH By: A6M5b, N1K2-J
Ho-5
Projectile Diameter: 20mm
Projectile Type: HEI
Projectile Weight gm: 79
Muzzle Velocity: 730 m/sec
Joules at the Muzzle: 21,000
Used in AH By: Ki-61-KAI-C
MG151/20
Projectile Diameter: 20mm
Projectile Type: HE
Projectile Weight gm: 115
Muzzle Velocity: 710 m/sec
Joules at the Muzzle: 29,000
Used in AH By: Bf109F-4, Bf109G-2, Bf109G-6, Bf109G-10, Fw190A-5, Fw190A-8, Fw190D-9, Fw190F-8, Ta152H-1
MG-FF
Projectile Diameter: 20mm
Projectile Type: HE
Projectile Weight gm: 134
Muzzle Velocity: 600 m/sec
Joules at the Muzzle: 24,100
Used in AH By: Fw190A-5
.50" Browning
Projectile Diameter: 12.7mm
Projectile Type: AP
Projectile Weight gm: 46
Muzzle Velocity: 880 m/sec
Joules at the Muzzle: 17,800
Used in AH By: B-17G, B-26B, Elco 80' PT Boat, F4U-1, F4U-1D, F6F-5, Lancaster MkIII, LTVA2, LTVA4, M3, M8 'Greyhound', M16, P-38L, P-47D-11, P-47D-25, P-47D-30, P-51B, P-51D, Spitfire MkIX