In 0.9.9.7, there seems to be a sort of LOS issue with aiming and firing a weapon.
When Im firing around corners of pillars, sometimes there's a gap in the firing sight. I pushed a barrel into that "missing" square and fired repeatedly using a pistol, and it never seemed to hit the barrel.
Moving the barrel to the targeted square ensued a hasty explosion.
 Fire -- Choose target...                                                       
 You see : out of vision                                                        
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  Patrick                    Armor : green armor [1/1] (40%)                    
  Health: 97%  Exp:  3/53%   Weapon: chaingun (1d6)x4 [40/40]                   
  cautious                                                    Phobos       Lev3 
With barrel:
 Fire -- Choose target...                                                       
 You see : out of vision                                                        
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 ############################################################################## 
  Patrick                    Armor : green armor [1/1] (40%)                    
  Health: 110% Exp:  3/55%   Weapon: chaingun (1d6)x4 [20/40]                   
  cautious                                                    Phobos       Lev3