The sights are not lined up. To fix this, edit weapons_smg_mk2.meta in
mods\update\x64\dlcpacks\mpgunrunning\dlc.rpf\common\data\ai

Search "FirstPersonScopeOffset" and replace the row with this

<FirstPersonScopeOffset x="0.000000" y="0.075000" z="-0.015300" />