The Solothurn S18-100 fires the 20x105mmB cartridge with a muzzle velocity of about 700m/s and penetrates roundabout 30-35mm RHA.
Meanwhile the ingame stats show a muzzle velocity of 900m/s and the ability to penetrate 50mm. Both values are way to high for the S18-100, but are the exact values for the upgraded version - the S18-1000 (20x138mmB, 900m/s, 50mm pen).
I suggest to have a look at it and add a “0” to the name (as a quick fix).
With best regards.