I would like to know, if possible, how resilant is the case or frame of a firearm. I'm specifically speaking of heavy caliber weapons such as machine guns, anti-materiel rifles, automatic grenade launchers, you name it. First, can a portable firearm, like a pistol, or an assault rifle (shotgun buckshot included. Breacher rounds excluded) severely damage one of the guns mentioned above? Second, if they can, can they do the same regardless of range, within the weapon's effective range? Then, in the hypothetic case you must shot from a distance, what are your chances to achieve a sure shot against the targeted weapon's vital pieces? This within the capabilities given by infantry training, and combat experience. Thanks in advice.