With the Update 71 (Ninja Pack) OVK fixed a bunch of misaligned sights, which is cool.
But it seems they kind of messed up the Locomotive and the Reinfeld, which is not cool.
This mod reverts the sight back to the old one so you can actually see something if you have a stock on your beloved shotgun (#locomasterrace).
Upon request, I tweaked the Mosconi ADS to be more horizontal. Add this at the end of the function PlayerTweakData:_init_new_stances, inside playertweakdata.lua.
Installation : extract in your Payday2/mods folder. You need BLT.