Bacalov Corrector

The Bacalov Corrector ingame version is a fictional variant of "Thompson Contender" that fires 20 rounds High Explosive bullets of unknown caliber and is a single-shot break-open breach-loading weapon. It comes pre-equipped with a scope, albeit one that has only a single level of zoom. Ammo for it is very scarce.

External link
Thompson/Center Contender on Wikipedia